Receivables, Net (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Net Revenue									$ 48,500,000
Accounts Notes Loans and Financing Receivable Gross Current	$ 341,186,000				$ 311,225,000				341,186,000	$ 311,225,000
Allowance for Accounts Notes Loans and Financing Receivable Current	364,000				291,000				364,000	291,000
Receivables, net	340,822,000				310,934,000				340,822,000	310,934,000
Revenue, Net	630,162,000	$ 751,376,000	$ 569,242,000	$ 420,249,000	589,789,000	$ 719,764,000	$ 585,870,000	$ 379,847,000	2,371,029,000	2,275,270,000	$ 2,266,901,000
Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revenue, Net									1,262,675,000	1,186,445,000	1,251,197,000
Large Project Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revenue, Net									812,720,000	825,044,000	$ 777,811,000
Construction Contracts [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Notes Loans and Financing Receivable Gross Current	298,426,000				275,854,000				298,426,000	275,854,000
Completed and in Progress [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Notes Loans and Financing Receivable Gross Current	206,756,000				191,094,000				206,756,000	191,094,000
Retentions [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Notes Loans and Financing Receivable Gross Current	91,670,000				84,760,000				91,670,000	84,760,000
Escrow [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Notes Loans and Financing Receivable Gross Current	21,958,000				28,692,000				21,958,000	28,692,000
Non Escrow [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Notes Loans and Financing Receivable Gross Current	69,712,000				56,068,000				69,712,000	56,068,000
Non-escrow retention receivables	0				8,600,000				0	8,600,000
Construction Material Sales [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Notes Loans and Financing Receivable Gross Current	28,727,000				28,549,000				28,727,000	28,549,000
Other Business Products and Services [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Notes Loans and Financing Receivable Gross Current	$ 14,033,000				$ 6,822,000				$ 14,033,000	$ 6,822,000
Government [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage Of Revenue Attributable to Counterparty									82.80%	84.80%	83.10%
Government [Member] | Construction And Large Project Contruction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total revenue from reportable segments									$ 1,700,000,000
New York State Department of Transportation [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revenue, Net									$ 199,000,000
Percentage Of Revenue Attributable to Counterparty									8.40%
New York State Department of Transportation [Member] | Large Project Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage Of Revenue Attributable to Counterparty									24.50%
California Department of Transportation [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revenue, Net										$ 195,400,000	$ 265,800,000
Percentage Of Revenue Attributable to Counterparty										8.60%	11.70%
California Department of Transportation [Member] | Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revenue, Net										$ 178,700,000	$ 239,900,000
Percentage Of Revenue Attributable to Counterparty										15.10%	19.20%
California Department of Transportation [Member] | Large Project Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revenue, Net										$ 16,800,000	$ 25,900,000
Percentage Of Revenue Attributable to Counterparty										2.00%	3.30%