Receivables, Net - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revenue, Net	$ 892,325	$ 1,055,591	$ 807,119	$ 563,379	$ 801,274	$ 957,126	$ 762,913	$ 468,400	$ 3,318,414	$ 2,989,713	$ 2,514,617
Uncollectible Receivables [Member] | Retentions [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Notes Loans and Financing Receivable Gross Current	$ 0				$ 0				0	0
California Department of Transportation [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revenue, Net									$ 282,900	$ 281,700	$ 222,400
Percentage of revenue attributable to counterparty									8.50%	9.40%	8.80%