Increase in gross margin percentage recognized as a result of revised cost estimates.

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- Definition

Represents the amount of deductible under health insurance benefits for qualified individuals.

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Represents the amount of deductible up to the claim aggregate under insurance arrangements, for each line of coverage excluding auto liability and medical insurance, excluding health insurance.

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- Definition

Represents the number of customers individually exceeding ten percent of consolidated accounts receivable.

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Represents the number of customers individually exceeding ten percent of consolidated revenues.

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Represents the percentage of retainage of long-term contracts recorded and expected to be collected by the entity within one year.

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No definition available.

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- Definition

Amount charged to advertising expense for the period, which are expenses incurred with the objective of increasing revenue for a specified brand, product or product line.

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- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

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The net result for the period of deducting operating expenses from operating revenues.

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Organization, Business and Significant Accounting Policies (Details Textual) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Organization Consolidation and Presentation of Financial Statements [Line Items]
Operating Income (Loss)									$ 58,404,000us-gaap_OperatingIncomeLoss	$ 55,617,000us-gaap_OperatingIncomeLoss	$ 55,762,000us-gaap_OperatingIncomeLoss
Net Income (Loss) Attributable to Parent	14,127,000us-gaap_NetIncomeLoss	8,404,000us-gaap_NetIncomeLoss	7,741,000us-gaap_NetIncomeLoss	6,272,000us-gaap_NetIncomeLoss	10,022,000us-gaap_NetIncomeLoss	8,315,000us-gaap_NetIncomeLoss	9,462,000us-gaap_NetIncomeLoss	6,960,000us-gaap_NetIncomeLoss	36,544,000us-gaap_NetIncomeLoss	34,759,000us-gaap_NetIncomeLoss	34,262,000us-gaap_NetIncomeLoss
Earnings Per Share, Diluted	$ 0.66us-gaap_EarningsPerShareDiluted	$ 0.39us-gaap_EarningsPerShareDiluted	$ 0.36us-gaap_EarningsPerShareDiluted	$ 0.29us-gaap_EarningsPerShareDiluted	$ 0.46us-gaap_EarningsPerShareDiluted	$ 0.38us-gaap_EarningsPerShareDiluted	$ 0.44us-gaap_EarningsPerShareDiluted	$ 0.32us-gaap_EarningsPerShareDiluted	$ 1.69us-gaap_EarningsPerShareDiluted	$ 1.61us-gaap_EarningsPerShareDiluted	$ 1.60us-gaap_EarningsPerShareDiluted
Number of Reportable Segments									2us-gaap_NumberOfReportableSegments
Advertising Expense									400,000us-gaap_AdvertisingExpense	300,000us-gaap_AdvertisingExpense	500,000us-gaap_AdvertisingExpense
Percentage Of Retainage Recorded And Collected Within One Year									90.00%
Loss Contingency Insurance Policy Deductible for Each Line of Coverage Excluding Health	1,000,000								1,000,000
Loss Contingency Health Insurance Deductible For Qualified Individuals	100,000								100,000
Accounts Receivable [Member] \| Number of Customers [Member]
Organization Consolidation and Presentation of Financial Statements [Line Items]
Concentration Risk, Percentage									10.00%	10.00%
Accounts Receivable [Member] \| Number of Customers [Member] \| Credit Concentration Risk [Member]
Organization Consolidation and Presentation of Financial Statements [Line Items]
Concentration Risk, Percentage									14.20%	14.40%
Number Of Customers Individually Exceeding Ten Percent Consolidated Accounts Receivable									1	1
Revenues [Member] \| Number of Customers [Member] \| Customer concentration risk [Member]
Organization Consolidation and Presentation of Financial Statements [Line Items]
Concentration Risk, Percentage											15.10%
Number Of Customers Individually Exceeding Ten Percent Consolidated Revenues											1
Revenues [Member] \| Top Ten Customers [Member] \| Customer concentration risk [Member]
Organization Consolidation and Presentation of Financial Statements [Line Items]
Concentration Risk, Percentage									46.50%	57.80%	59.60%
Labor employees covered by collective bargaining agreements [Member] \| Labor Force Concentration Risk [Member]
Organization Consolidation and Presentation of Financial Statements [Line Items]
Concentration Risk, Percentage									91.00%
Contracts Accounted for under Percentage of Completion [Member] \| Cost Estimate Revision [Member]
Organization Consolidation and Presentation of Financial Statements [Line Items]
Cost Estimate Revision Gross Margin Increase Percentage									1.90%	0.80%
Estimate Adjustment [Member]
Organization Consolidation and Presentation of Financial Statements [Line Items]
Operating Income (Loss)									18,400,000	7,700,000
Net Income (Loss) Attributable to Parent									$ 11,600,000	$ 4,900,000
Earnings Per Share, Diluted									$ 0.54	$ 0.23