Summary of Significant Accounting Policies - Revenue Recognition (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Contracts in progress
Costs incurred on contracts in progress	$ 2,518,581	$ 1,574,460
Estimated earnings, net of losses	405,891	300,514
Less-Billings to date	(3,033,112)	(1,958,567)
Less-Unbilled accounts receivable	(55,542)	(37,180)
Contracts in progress	(164,182)	(120,773)
Costs and estimated earnings in excess of billings	2,736	10,213	$ 30,116
Billings in excess of costs and estimated earnings	$ (166,918)	(130,986)	$ (106,005)
Period during which progress billings or contract price can be withheld until completion of work	6 months
Retention receivable	$ 111,700	80,800
Retention payable	$ 15,800	$ 13,700
Revenue, Performance Obligation, Description of Payment Terms	We typically invoice our customers with payment terms of net due in 30 days
Receivable payment terms (in days)	30 days
Minimum
Contracts in progress
Receivable payment terms (in days)	45 days
Payments received term (in days)	30 days
Maximum
Contracts in progress
Receivable payment terms (in days)	60 days
Payments received term (in days)	90 days