CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017
Cash and cash equivalents	$ 230,259	$ 233,711	$ 185,516
Receivables, Net	618,070	479,791	627,081
Contract assets	213,989	0	0
Costs and estimated earnings in excess of billings	0	103,965	94,527
Other current assets	32,185	36,513	26,612
Property and equipment, net	560,618	407,418	412,174
Accounts payable	316,917	237,673	286,913
Contract liabilities	117,759	0	0
Billings in excess of costs and estimated earnings	0	135,146	168,707
Accrued expenses and other current liabilities	$ 296,033	$ 236,407	$ 246,775
Preferred Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01	$ 0.01
Preferred Stock, Shares Authorized	3,000,000	3,000,000	3,000,000
Preferred Stock, Shares Outstanding	0	0	0
Common Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01	$ 0.01
Common Stock, Shares Authorized	150,000,000	150,000,000	150,000,000
Common Stock, Shares, Issued	46,897,092	39,871,314	39,850,587
Common Stock, Shares, Outstanding	46,897,092	39,871,314	39,850,587
Consolidated Construction Joint Venture [Member] | Joint Venture Consolidated [Member]
Cash and cash equivalents	$ 125,165	$ 94,359	$ 71,328
Receivables, Net	26,142	52,031	51,079
Contract assets	20,968	0	0
Costs and estimated earnings in excess of billings	0	1,437	3,035
Other current assets	11,361	10,384	6,033
Property and equipment, net	36,061	38,361	33,754
Accounts payable	33,426	34,795	27,443
Contract liabilities	67,139	0	0
Billings in excess of costs and estimated earnings	0	37,701	38,581
Accrued expenses and other current liabilities	$ 1,975	$ 2,126	$ 1,354