Document and Entity Information Statement [Table] Statement [Line Items] Statement Entity Registrant Name Entity Central Index Key Document Type Document Period End Date Document Fiscal Year Focus Document Fiscal Period Focus Amendment Flag Current Fiscal Year End Date Entity Current Reporting Status Entity Filer Category Entity Small Business Entity Emerging Growth Company Entity Common Stock, Shares Outstanding CONSOLIDATED BALANCE SHEETS Assets [Abstract] ASSETS Assets, Current [Abstract] CURRENT ASSETS: Cash and Cash Equivalents, at Carrying Value CASH AND CASH EQUIVALENTS, end of year CASH AND CASH EQUIVALENTS, beginning of year Cash and cash equivalents Billed Contracts Receivable Billed accounts receivable, less allowance for doubtful accounts of $5,865 and $5,898, respectively Unbilled Contracts Receivable Unbilled accounts receivable Nontrade Receivables, Current Other receivables Inventory, Net Inventories Prepaid Expense and Other Assets, Current Prepaid expenses and other Contract with Customer, Asset, Net, Current Balance at end of period Balance at beginning of period Costs and estimated earnings in excess of billings Assets, Current Total current assets Property, Plant and Equipment, Net PROPERTY AND EQUIPMENT, NET Operating Lease, Right-of-Use Asset LEASE RIGHT-OF-USE ASSET Lease right-of-use assets Goodwill. Balance at end of period Balance at beginning of year GOODWILL Intangible Assets, Net (Excluding Goodwill) IDENTIFIABLE INTANGIBLE ASSETS, NET Deferred Tax Assets, Net, Noncurrent DEFERRED TAX ASSETS Other Assets, Noncurrent OTHER NONCURRENT ASSETS Assets Total assets Liabilities and Equity [Abstract] LIABILITIES AND STOCKHOLDERS' EQUITY Liabilities, Current [Abstract] CURRENT LIABILITIES: Less- Current portion Less-current portion Current maturities of long-term debt Accounts Payable, Current Accounts payable Employee-related Liabilities, Current Accrued compensation and benefits Contract with Customer, Liability, Current Balance at end of period Balance at beginning of period Billings in excess of costs and estimated earnings Self Insurance Reserve, Current Accrued self-insurance Other Liabilities, Current Other current liabilities Liabilities, Current Total current liabilities Long-term Debt, Excluding Current Maturities LONG-TERM DEBT Operating Lease, Liability, Noncurrent Lease liabilities LONG-TERM LEASE LIABILITIES Deferred Tax Liabilities, Net, Noncurrent DEFERRED TAX LIABILITIES Other Liabilities, Noncurrent OTHER LONG-TERM LIABILITIES Liabilities Total liabilities Commitments and Contingencies. COMMITMENTS AND CONTINGENCIES Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] STOCKHOLDERS' EQUITY: Preferred Stock, Value, Issued Preferred stock, $.01 par, 5,000,000 shares authorized, none issued and outstanding Common Stock, Value, Issued Common stock, $.01 par, 102,969,912 shares authorized, 41,123,365 and 41,123,365 shares issued, respectively Treasury Stock, Value Treasury stock, at cost, 4,232,418 and 4,229,653 shares, respectively Additional Paid in Capital, Common Stock Additional paid-in capital Retained Earnings (Accumulated Deficit) Retained earnings Stockholders' Equity Attributable to Parent BALANCE BALANCE Total stockholders' equity Liabilities and Equity Total liabilities and stockholders' equity Balance at beginning of year Accounts receivable, allowance for doubtful accounts (in dollars) Preferred Stock, Par or Stated Value Per Share Preferred stock, par value (in dollars per share) Preferred Stock, Shares Authorized Preferred stock, shares authorized Preferred Stock, Shares Issued Preferred stock, shares issued Preferred Stock, Shares Outstanding Preferred stock, shares outstanding Common Stock, Par or Stated Value Per Share Common stock, par value (in dollars per share) Common Stock, Shares Authorized Common stock, shares authorized Common Stock, Shares, Issued BALANCE (in shares) BALANCE (in shares) Common stock, shares issued Treasury Stock, Shares BALANCE (in shares) BALANCE (in shares) Treasury stock, shares CONSOLIDATED STATEMENTS OF OPERATIONS Revenues REVENUE Cost of Revenue COST OF SERVICES Gross Profit Gross profit Selling, General and Administrative Expense SELLING, GENERAL AND ADMINISTRATIVE EXPENSES Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property GAIN ON SALE OF ASSETS Operating Income (Loss) Operating income Nonoperating Income (Expense) [Abstract] OTHER INCOME (EXPENSE): Investment Income, Interest Interest income Total. Interest expense Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability Changes in the fair value of contingent earn-out obligations Changes in the fair value of contingent earn-out obligations Other Nonoperating Income (Expense) Other Nonoperating Income (Expense) Other income (expense) Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest INCOME BEFORE INCOME TAXES Income Tax Expense (Benefit) Provision for income taxes PROVISION FOR INCOME TAXES Net Income (Loss) Attributable to Parent NET INCOME Earnings Per Share [Abstract] INCOME PER SHARE: Net income (loss) (in dollars per share) Basic (in shares) Net diluted income after-tax (in dollars per share) Diluted (in shares) Weighted Average Number of Shares Outstanding, Diluted [Abstract] SHARES USED IN COMPUTING INCOME PER SHARE: Weighted Average Number of Shares Outstanding, Basic Basic (in shares) Shares used in computing earnings per share-basic Weighted Average Number of Shares Outstanding, Diluted Diluted (in shares) Shares used in computing earnings per share-diluted Common Stock, Dividends, Per Share, Declared DIVIDENDS PER SHARE (in dollars per share) CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Common Stock [Member] Common Stock Treasury Stock [Member] Treasury Stock Additional Paid In Capital [Member] Additional Paid-In Capital Retained Earnings [Member] Retained Earnings Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Net income Net income Stock Issued or Granted During Period, Share-based Compensation [Abstract] Issuance of Stock: Stock Issued During Period, Value, Stock Options Exercised Issuance of shares for options exercised Exercised (in shares) Issuance of shares for options exercised (in shares) Aggregate value of stock related to Restricted and Performance Stock Awards issued during the period. Stock Issued During Period Value Restricted And Performance Stock Award Gross Issuance of restricted stock & performance stock Total number of shares issued during the period, including shares forfeited, as a result of Restricted and Performance Stock Awards. Stock Issued During Period, Shares, Restricted And Performance Stock Award Gross Issuance of restricted stock & performance stock (in shares) Adjustments Related to Tax Withholding for Share-based Compensation Shares received in lieu of tax withholding payment on vested restricted stock Shares Paid for Tax Withholding for Share Based Compensation Shares received in lieu of tax withholding payment on vested restricted stock (in shares) Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition Stock-based compensation Dividends, Common Stock, Cash Dividends Treasury Stock, Value, Acquired, Cost Method Share repurchase Treasury Stock, Shares, Acquired Share repurchase (in shares) CONSOLIDATED STATEMENTS OF CASH FLOWS Net Cash Provided by (Used in) Operating Activities [Abstract] CASH FLOWS FROM OPERATING ACTIVITIES: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Adjustments to reconcile net income to net cash provided by operating activities- Amortization of Intangible Assets Amortization of identifiable intangible assets Depreciation Depreciation expense Provision for Doubtful Accounts Bad debt expense Deferred Income Tax Expense (Benefit) Deferred tax provision Amortization of Financing Costs Amortization of debt financing costs Gain (Loss) on Disposition of Property Plant Equipment Gain on sale of assets Share-based Compensation Stock-based compensation Increase (Decrease) in Operating Capital [Abstract] Changes in operating assets and liabilities, net of effects of acquisitions and divestitures- Increase (Decrease) in Operating Assets [Abstract] (Increase) decrease in- Increase (Decrease) in Accounts Receivable Receivables, net Increase (Decrease) in Inventories Inventories Increase (Decrease) in Prepaid Expense and Other Assets Prepaid expenses and other current assets The increase (decrease) during the reporting period in contract with customer assets. Increase Decrease in Contract with Customer Assets Costs and estimated earnings in excess of billings and unbilled accounts receivable Increase (Decrease) in Other Operating Assets Other noncurrent assets Increase (Decrease) in Operating Liabilities [Abstract] Increase (decrease) in- Increase (Decrease) in Accounts Payable and Accrued Liabilities Accounts payable and accrued liabilities Increase Decrease in Contract with Customer Liability Billings in excess of costs and estimated earnings Increase (Decrease) in Other Operating Liabilities Other long-term liabilities Net Cash Provided by (Used in) Operating Activities Net cash provided by operating activities Net Cash Provided by (Used in) Investing Activities [Abstract] CASH FLOWS FROM INVESTING ACTIVITIES: Payments to Acquire Property, Plant, and Equipment Purchases of property and equipment Proceeds from Sale of Property, Plant, and Equipment Proceeds from sales of property and equipment Payments to Acquire Businesses, Net of Cash Acquired Cash paid for acquisitions, net of cash acquired Net Cash Provided by (Used in) Investing Activities Net cash used in investing activities Net Cash Provided by (Used in) Financing Activities [Abstract] CASH FLOWS FROM FINANCING ACTIVITIES: Proceeds from Long-term Lines of Credit Proceeds from revolving line of credit Repayments of Long-term Lines of Credit Payments on revolving line of credit Repayments of Other Debt Payments on other debt Payments of Ordinary Dividends, Common Stock Payments of dividends to stockholders Payments for Repurchase of Common Stock Share repurchase Share repurchase Payments Related to Tax Withholding for Share-based Compensation Shares received in lieu of tax withholding Proceeds from Stock Options Exercised Proceeds from exercise of options Deferred acquisition payments. Deferred Acquisition Payments Deferred acquisition payments Payment for Contingent Consideration Liability, Financing Activities Payments for contingent consideration arrangements Net Cash Provided by (Used in) Financing Activities Net cash used in financing activities Cash and Cash Equivalents, Period Increase (Decrease) NET DECREASE IN CASH AND CASH EQUIVALENTS Business and Organization Nature of Operations [Text Block] Business and Organization Summary of Significant Accounting Policies Basis of Presentation and Significant Accounting Policies [Text Block] Summary of Significant Accounting Policies Fair Value Measurements Fair Value Disclosures [Text Block] Fair Value Measurements Acquisitions Business Combination Disclosure [Text Block] Acquisitions Goodwill Goodwill and Intangible Assets Disclosure [Text Block] Goodwill Debt Obligations Long-term Debt [Text Block] Debt Obligations Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Commitments and Contingencies Stockholders' Equity Stockholders' Equity Note Disclosure [Text Block] Stockholders' Equity. Subsequent Events Subsequent Events [Text Block] Subsequent Events Basis of Accounting, Policy [Policy Text Block] Basis of Presentation Use of Estimates, Policy [Policy Text Block] Use of Estimates New Accounting Pronouncements, Policy [Policy Text Block] Recent Accounting Pronouncements Revenue from Contract with Customer [Policy Text Block] Revenue Recognition Lessee, Leases [Policy Text Block] Leases Receivables, Policy [Policy Text Block] Accounts Receivable Income Tax, Policy [Policy Text Block] Income Taxes Fair Value of Financial Instruments, Policy [Policy Text Block] Financial Instruments Segment Reporting, Policy [Policy Text Block] Segment Disclosure Disaggregation of Revenue [Table Text Block] Schedule of disaggregation or revenue Contract with Customer, Asset and Liability [Table Text Block] Schedule of contract assets and liabilities Tabular disclosure of lease assets and liabilities. Schedule of Lease Assets and Liabilities [Table Text Block] Schedule of lease asset and liabilities Lessee, Operating Lease, Liability, Maturity [Table Text Block] Schedule of maturities of lease liabilities Tabular disclosure of supplemental information related to leases. Schedule of Supplemental Information Related to Leases [Table Text Block] Schedule of supplemental information related to leases Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Summary of fair values and levels within the fair value hierarchy in which the fair value measurements fall for assets and liabilities measured on a recurring basis Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block] Schedule of reconciliation of the fair value of contingent earn-out obligations that use significant unobservable inputs (Level 3) Schedule of Goodwill [Table Text Block] Schedule of changes in the carrying amount of goodwill Schedule of Debt [Table Text Block] Schedule of components of debt obligations Tabular disclosure of the additional margins added to the reference rate to compute the variable rate on the debt instrument. Schedule of Additional Margins [Table Text Block] Summary of additional margins Schedule of Weighted Average Number of Shares [Table Text Block] Reconciliation of number of shares outstanding with the number of shares used in computing basic and diluted earnings per share Schedule of information related to the business and organization. Schedule of Business and Organization [Table] Products and Services [Axis] Products And Services [Domain] Products and Services [Domain] Represents information pertaining to installation of systems in newly constructed facilities. System Installation In Newly Constructed Facilities [Member] Installation of systems in newly constructed facilities Represents information pertaining to maintenance, repair and replacement services. Maintenance Repair And Replacement Service [Member] Maintenance, repair and replacement services Schedule of Business and Organization [Line Items] Business and Organization The percentage of net services revenue to total net revenue from the services rendered as of the year end. Sales Revenue Services Net Percentage Percentage of revenue attributable to services New Accounting Pronouncements or Change in Accounting Principle [Table] New Accounting Pronouncements or Change in Accounting Principle Operating Lease, Liability Operating lease liability Present Value of Lease Liabilities Disaggregation of Revenue [Table] Disaggregation of Revenue [Line Items] Disaggregation of Revenue Revenue, Performance Obligation, Description of Payment Terms The payment terms for receivables in days. Receivable Due Term Receivable payment terms (in days) The number of days in which the entity receives payment from customers. Payments Received Term Payments received term (in days) Revenue from Contract with Customer, Excluding Assessed Tax Revenue The percentage of revenue from contract with customers. Percentage of Revenue from Contract With Customer Percentage of revenue from contract with customer (as a percent) Revenue, Initial Application Period Cumulative Effect Transition [Table] Revenue, Initial Application Period Cumulative Effect Transition [Line Items] Change in Contract with Customer, Asset [Abstract] Contract Assets Contract with Customer, Asset, Increase (Decrease) for Contract Acquired in Business Combination Change due to acquisitions Amount of increase (decrease) in contract with customer assets due to change in conditional versus unconditional. Contract with Customer, Asset, Increase (Decrease) for Change Due to Conditional Versus Unconditional Change due to conditional versus unconditional Contract with Customer, Asset, Reclassified to Receivable Reclassified to unbilled accounts receivable Change in Contract with Customer, Liability [Abstract] Contract Liabilities Contract with Customer, Liability, Increase (Decrease) for Contract Acquired in Business Combination Change due to acquisitions Contract with Customer, Liability, Change in Timeframe, Performance Obligation Satisfied, Revenue Recognized Change in timing for performance obligation to be satisfied Contract with Customer, Liability, Revenue Recognized Revenue related to our contract liabilities Contract with Customer, Asset, Credit Loss Expense Impairment losses Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] Remaining Performance Obligations Revenue, Remaining Performance Obligation Remaining performance obligations Revenue, Remaining Performance Obligation, Percentage Expected percentage of remaining performance obligations Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period Expected timing of performance obligations The term of renewable service maintenance agreements in years. Renewable Service Maintenance Agreements Term The term of the renewable service maintenance agreements (in years) Lessee, Lease, Description [Table] Lessee, Lease, Description [Line Items] Amount of variable lease cost and short-term lease cost, excluded from lease liability, recognized when obligation for payment is incurred for finance and operating leases. Variable Lease and Short-term Lease, Cost Variable lease expense and short-term lease expenses Operating Lease, Weighted Average Discount Rate, Percent Weighted average discount rate Operating Lease, Expense Lease expense Lessee, Operating Lease, Term of Contract Lease term Represents the number of options to renew. Number of Options to Renew Number of options to renew Operating Lease, Weighted Average Remaining Lease Term Weighted average remaining lease term Payments for Rent Rent paid to related parties Lessee, Operating Lease, Existence of Option to Extend [true false] Existence of option to extend Assets and Liabilities, Lessee [Abstract] Summary of lease asset and liabilities No definition available. Lease Liabilities [Abstract] Lease Liabilities Operating Lease, Liability, Current Other current liabilities Operating Lease, Liability, Current, Statement of Financial Position [Extensible List] Operating Lease Liabilities, Payments Due [Abstract] Maturities of lease liabilities: Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year 2019 (excluding the three months ended March 31, 2019) Lessee, Operating Lease, Liability, Payments, Due Year Two 2020 Lessee, Operating Lease, Liability, Payments, Due Year Three 2021 Lessee, Operating Lease, Liability, Payments, Due Year Four 2022 Lessee, Operating Lease, Liability, Payments, Due Year Five 2023 Lessee, Operating Lease, Liability, Payments, Due after Year Five Thereafter Lessee, Operating Lease, Liability, Payments, Due Total Lease Payments Lessee, Operating Lease, Liability, Undiscounted Excess Amount Less-Interest No definition available. Supplemental Information Related to Leases [Abstract] Supplemental information related to leases: Operating Lease, Payments Cash paid for amounts included in the measurement of lease liabilities Right-of-Use Asset Obtained in Exchange for Operating Lease Liability Lease right-of-use assets obtained in exchange for lease liabilities Increase (Decrease) in Income Taxes Payable Provision for income taxes Fair Value Measurements, Recurring and Nonrecurring [Table] Measurement Frequency [Axis] Fair Value Measurement Frequency [Domain] Fair Value, Measurement Frequency [Domain] Fair Value Measurements Recurring [Member] Recurring basis Fair Value, Hierarchy [Axis] Fair Value Measurements Fair Value Hierarchy [Domain] Fair Value Hierarchy [Domain] Fair Value Inputs Level1 [Member] Quoted Market Prices In Active Markets for Identical Assets (Level 1) Fair Value Inputs Level2 [Member] Fair Value Measurements at Reporting Date Using Significant Other Observable Inputs (Level 2) Fair Value Inputs Level3 [Member] Significant Unobservable Inputs (Level 3) Liability Class [Axis] Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation By Liability Class [Domain] Fair Value by Liability Class [Domain] Represents the information pertaining to the contingent consideration obligations that have been provided in a business combination. Contingent Consideration Obligations [Member] Contingent earn-out obligations Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value Measurements Cash and Cash Equivalents, Fair Value Disclosure Cash and cash equivalents Cash Surrender Value, Fair Value Disclosure Life insurance-cash surrender value Fair value, as of the balance sheet date, of potential cash payments under the contingent consideration arrangement. Business Acquisition Contingent Consideration Fair Value at Balance Sheet Date Contingent earn-out obligations Represents the number of employees covered under life insurance policy contracts. Life Insurance Contracts Number of Employees Covered Number of employees covered under life insurance policies Represents the face amount of life insurance policies taken by the entity for their employees. Life Insurance Contracts Face Amount Combined face value of life insurance policies Cash Surrender Value of Life Insurance Cash surrender value Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] Reconciliation of the fair value of contingent earn-out obligations that use significant unobservable inputs (Level 3) Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Value Balance at end of period Balance at beginning of year Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Issuances Issuances Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements Settlements Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings Adjustments to fair value Schedule of Business Acquisitions, by Acquisition [Table] Business Acquisition [Line Items] Acquisitions Business Combination, Consideration Transferred Total purchase price Number of Businesses Acquired Number of acquisitions The number of businesses acquired by the entity during the period that are reported as a separate operating location. Number Of Acquisitions Reported As Separate Operations Number of acquisitions reported as separate operating location Schedule of Goodwill [Table] Goodwill [Line Items] Goodwill Goodwill [Roll Forward] Changes in the carrying amount of goodwill Goodwill, Acquired During Period Additions (See Note 4) Schedule of Long-term Debt Instruments [Table] Debt Instrument [Axis] Debt Instrument Name [Domain] Debt Instrument, Name [Domain] Notes Payable Other Payables [Member] Other debt Subordinated Debt [Member] Subordinate note Revolving Credit Facility [Member] Revolving credit facility Debt Instrument [Line Items] Debt Obligations Notes and Loans Payable Outstanding balance Debt, Long-term and Short-term, Combined Amount Total debt Total Debt Total long-term portion of debt Outstanding balance Information pertaining to the amended senior revolving credit facility. Amended Senior Revolving Credit Facility [Member] Amended senior revolving credit facility This element represents domestic or foreign subordinated debt and promissory note. Subordinated debt has a lower priority of repayment in liquidation of the entity's assets and promissory notes has a borrowing supported by a written promise to pay an obligation. Subordinate Debt And Promissory Note [Member] Notes to former owners Variable Rate [Axis] Variable Rate [Domain] Variable Rate [Domain] The base rate used to calculate the variable interest rate of the debt instrument. Debt Instrument Variable Rate Base Rate [Member] Base Rate Eurodollar [Member] Eurodollar Rate Range [Axis] Range [Member] Range [Domain] Minimum [Member] Minimum Maximum [Member] Maximum Information by different ratios applicable to debt covenants. Debt Covenant Ratio [Axis] Groups of debt covenant ratio ranges. Debt Covenant Ratio [Domain] Debt Covenant Ratio [Domain] Represents activity related to range one of specified debt covenant. Debt Covenant Ratio Range One [Member] Consolidated Total Indebtedness to Credit Facility Adjusted EBITDA: Less than 1.00 Represents activity related to range two of specified debt covenant. Debt Covenant Ratio Range Two [Member] Consolidated Total Indebtedness to Credit Facility Adjusted EBITDA: 1.00 to 1.75 Represents activity related to range three of specified debt covenant. Debt Covenant Ratio Range Three [Member] Consolidated Total Indebtedness to Credit Facility Adjusted EBITDA: 1.75 to 2.50 Represents activity related to range four of specified debt covenant. Debt Covenant Ratio Range Four [Member] Consolidated Total Indebtedness to Credit Facility Adjusted EBITDA: 2.50 or greater Scenario [Axis] Scenario Unspecified [Domain] Scenario, Unspecified [Domain] Domain member used to indicate the requirements per the terms of the debt agreement. Scenario Covenant Requirement [Member] Covenant Requirement Member used to indicate the period during which stock repurchases are made. Stock Repurchases After February222016 And On Or Before December312017 [Member] Stock Repurchases After February 22, 2016 And On Or Before December 31, 2017 Information by date that the debt covenant ratio is applicable. Debt Covenant Effective Date [Axis] The period through which the debt covenant ratio is applicable. Debt Covenant Effective Date [Domain] Debt Covenant Effective Date [Domain] Represents information through the debt maturity date. Through Maturity [Member] Through maturity Line of Credit Facility, Maximum Borrowing Capacity Borrowing capacity Accordion option on credit facility per terms of the agreement. Line of credit borrowing capacity accordion option Line of Credit Facility, Amount Outstanding Outstanding borrowings Letters of Credit Outstanding, Amount Letters of credit amount outstanding Line of Credit Facility, Remaining Borrowing Capacity Credit available Reconciliation of Earnings before Interest Tax Depreciation and Amortization to Net Income Debt Instrument Financial Covenants [Abstract] Principal financial covenants Represents the number of interest rate options. Number of interest rate options Represents the ratio of consolidated total debt to consolidated adjusted earnings before, interest, taxes, depreciation and amortization required to be maintained under the financial covenants. Debt Instrument Covenant Leverage Ratio Leverage ratio Represents the ratio of consolidated adjusted earnings before, interest, taxes, depreciation and amortization, less non-financed capital expenditures, tax provision, dividends and amounts used to repurchase stock to the sum of interest expense and scheduled principal payments of indebtedness required to be maintained under the financial covenants. Debt Instrument Covenant Fixed Charge Coverage Ratio Fixed charge coverage ratio Represents the net leverage ratio used to determine exclusion of stock repurchases and the payment of dividends for calculation of the fixed charge coverage ratio under the financial covenants. Debt Instrument Covenant Net Leverage Ratio Used to Determine Exclusion of Stock Repurchases and Dividend Payments for Calculating Fixed Charge Coverage Ratio Net leverage ratio used to determine exclusion of stock repurchases and the payment of dividends for calculation of the fixed charge coverage ratio Represents the amount of stock repurchases to maintain maximum net leverage ratio. Debt Instrument Covenant Amount of Stock Repurchases to Maintain Maximum Net Leverage Ratio Amount of stock repurchases to maintain maximum net leverage ratio Represents the net leverage ratio determine after giving effect to stock repurchases for calculation of the fixed charge coverage ratio under the financial covenants. Debt Instrument Covenant Net Leverage Ratio after Giving Effect to Stock Repurchases for Calculating Fixed Charge Coverage Ratio Net leverage ratio after giving effect to stock repurchases for calculation of the fixed charge coverage ratio Represents the number of quarters of capital expenditures, tax provision, dividends and stock repurchase payments used for the calculation of the fixed charge coverage ratio. Debt Instrument Covenant Capital Expenditures Tax Provisions Dividends and Stock Repurchase Payments Used for Calculation of Fixed Charge Coverage Ratio Number of Quarters Number of quarters of capital expenditures, tax provision, dividends and stock repurchase payments used for calculation of fixed charge coverage ratio Represents the amount of acquisition per transaction permitted under the financial covenants. Debt Instrument Covenant Other Restrictions Permitted Acquisition Amount Per Transaction Permitted amount of acquisitions per transaction Represents the aggregate purchase price of current acquisition and acquisitions in the preceding twelve month period used for determining the permitted amount of acquisition per transaction under the financial covenants. Debt Instrument Covenant Other Restrictions Aggregate Purchase Price of Acquisitions Aggregate purchase price of current acquisition and acquisitions in the preceding 12 month period for determining permitted amount of acquisition per transaction Represents the net leverage ratio as defined in the financial covenants which is used as a basis to determine other restrictions. Debt Instrument Covenant Other Restrictions Net Leverage Ratio Net leverage ratio used as basis for other restrictions Debt Instrument Variable Rate [Abstract] Additional per annum interest margin added under: Interest rate margin (as a percent) Additional per annum interest margin (as a percent) Represents the fees for the letter of credit facility, expressed as a percent based on the ratio of consolidated total indebtedness to credit facility adjusted EBITDA, as defined in the credit agreement. Letter of Credit Fees Percentage Letter of credit fees (as a percent) Line of Credit Facility, Unused Capacity, Commitment Fee Percentage Commitment fees payable on unused portion of the facility (as a percent) Long-term Debt, Other Disclosures [Abstract] Other disclosures The cumulative number of companies acquired by the entity. Cumulative Number Of Companies Acquired Cumulative number of companies acquired Debt, Weighted Average Interest Rate Weighted average interest rate (as a percent) Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt Acquired debt Loss Contingencies [Table] Loss Contingency Nature [Axis] Loss Contingency Nature [Domain] Loss Contingency, Nature [Domain] Surety Bond [Member] Surety Loss Contingencies [Line Items] Commitments and Contingencies Loss Contingency Surety [Abstract] Surety Represents the percentage of business which has required bonds. Percentage of Business which has Required Bonds Percentage of business which has required bonds Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Stockholders' Equity Shares Repurchase Program [Abstract] Share Repurchase Program Stock Repurchase Program, Number of Shares Authorized to be Repurchased Number of shares of outstanding common stock authorized to be acquired under a stock repurchase program Treasury Stock Acquired, Average Cost Per Share Average price (in dollars per share) Plan Name [Axis] Plan Name [Domain] Plan Name [Domain] Information pertaining to the March 2007 stock repurchase program. Stock Repurchase Program2007 [Member] Stock Repurchase Program 2007 Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Antidilutive Securities [Axis] Antidilutive Securities Name [Domain] Antidilutive Securities, Name [Domain] An arrangement whereby an employee and other than employee is entitled to receive in the future, subject to vesting and other restrictions, a number of shares in the entity at a specified price, as defined in the agreement. Although there are variations, normally, after vesting, when an option is exercised, the employee-holder and non-employee-holder pays the strike value in cash to the issuing employer-entity and receives equity shares. The equity shares can be sold into the market for cash at the current market price without restriction. Employee And Nonemployee Stock Option [Member] Stock Options Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Earnings Per Share Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Anti-dilutive securities excluded from computation of earnings per share amount (in shares) Weighted Average Number of Shares Outstanding Reconciliation [Abstract] Reconciliation of the number of shares outstanding with the number of shares used in computing basic and diluted earnings per share Common Stock, Shares, Outstanding Common shares outstanding, end of period Represents the effect of using weighted average common shares outstanding. Effect of Using Weighted Average Common Shares, Outstanding Effect of using weighted average common shares outstanding Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements Effect of shares issuable under stock option plans based on the treasury stock method Incremental Common Shares Attributable to Dilutive Effect of Contingently Issuable Shares Effect of restricted and contingently issuable shares Subsequent Event [Table] Subsequent Event Type [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Subsequent Event [Member] Subsequent Event Subsequent Event [Line Items] Subsequent Events Payments to Acquire Businesses, Gross Purchase price paid in cash Business Combination, Consideration Transferred, Liabilities Incurred Promissory note payable Represents the number of installments to pay the liability. Business Combination, Number of Installments Number of equal installments Amount of each installment incurred by the acquirer as part of consideration transferred in a business combination. Business Combination, Consideration Transferred, Liabilities Incurred, Installment Amount Installment amount on third and fourth anniversaries Amount funded as of closing, as an advance that is expected to be recovered as part of the working capital settlement and other contingent future payments. Purchase Price Advance Purchase price advance Represents the net receivable (liability), as of the balance sheet date, for contracts in process in which contracts with billings in excess of costs are netted against contracts with costs in excess of billings. Contract Receivables Contracts in Process, Net Receivable Liability Adjustments for New Accounting Pronouncements [Axis] Type Of Adoption [Member] Type of Adoption [Domain] Accounting Standards Update201602 [Member] ASU 2016-02 This member stands for heating, ventilation and air conditioning and plumbing. Heating Ventilation And Air Conditioning And Plumbing [Member] HVAC and Plumbing Represents information pertaining to building automation control system services. Building Automation Control Systems [Member] Building Automation Control Systems Product And Service Other [Member] Other Customer [Axis] Name Of Major Customer [Domain] Customer [Domain] Building designed to house industrial operations and provide the necessary conditions for the operation of industrial equipment. Industrial Property Customer [Member] Industrial This members stands for education. Education [Member] Education Building designed primarily for the conduct of business, for example, but not limited to, administration, clerical services, and consultation. Office Building Customer [Member] Office Buildings Sector of the economy consisting of companies engaged in healthcare-related business activities. Healthcare Sector Customer [Member] Healthcare Organization that is the governing authority of a community. Government Customer [Member] Government This member stands for retail, restaurants and entertainment Retail Restaurants And Entertainment [Member] Retail, Restaurants and Entertainment This member stands for multi family and residential. Multi Family And Residential [Member] Multi-Family and Residential This member stands for other customer. Other Customer [Member] Other Segments [Axis] Segment [Domain] Segments [Domain] This member stands for new construction. New Construction [Member] New Construction This member stands for existing building construction. Existing Building Construction [Member] Existing Building Construction This member stands for service projects. Service Projects [Member] Service Projects This member stands for service calls, maintenance and monitoring. Service Calls Maintenance And Monitoring [Member] Service Calls, Maintenance and Monitoring Initial Application Period Cumulative Effect Transition [Axis] Initial Application Period Cumulative Effect Transition [Domain] Initial Application Period Cumulative Effect Transition [Domain] Calculated Under Revenue Guidance In Effect Before Topic606 [Member] Calculated under Revenue Guidance in Effect before Topic 606 [Member] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis] Measurement Basis [Axis] Portion At Fair Value Fair Value Disclosure [Member] Portion at Fair Value Measurement [Member] Estimate Of Fair Value Fair Value Disclosure [Member] Total Loans Payable [Member] Promissory note London Interbank Offered Rate L I B O R [Member] London Interbank Offered Rate (LIBOR) Business Acquisition [Axis] Business Acquisition Acquiree [Domain] Business Acquisition, Acquiree [Domain] Represents information from Shoffner Kalthoff Mechanical Electrical Service. Shoffner [Member] Shoffner Represents the information pertaining to BCH Holdings, Inc and each of its wholly-owned subsidiaries. Bch Holdings Inc [Member] BCH Represents information pertaining to the acquisition in the first quarter of 2019. Acquisition First Quarter2019 [Member] Acquisition First Quarter 2019 [Member] Represents information pertaining to the acquisition in the first quarter of 2018. Acquisition First Quarter2018 [Member] Acquisition First Quarter 2018 [Member] Represents information pertaining to the acquisition in the second quarter of 2018. Acquisition Second Quarter2018 [Member] Acquisition Second Quarter 2018 [Member] Represents information pertaining to the acquisition in the third quarter of 2018. Acquisition Third Quarter2018 [Member] Acquisition Third Quarter 2018 [Member] Represents information pertaining to a second acquisition in the third quarter of 2018. Acquisition Two Third Quarter2018 [Member] Acquisition Two Third Quarter 2018 [Member] Represents information pertaining to Walker TX Holdings, Inc. and its wholly-owned subsidiaries. Walker Tx Holdings Inc. And Its Wholly Owned Subsidiaries [Member] Walker