CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017
Cash and cash equivalents	$ 195,515	$ 233,711	$ 178,068
Receivables, Net	492,718	479,791	484,245
Contract assets	265,190	0	0
Costs and estimated earnings in excess of billings	0	103,965	99,883
Other current assets	49,100	36,513	43,597
Property and equipment, net	595,787	407,418	414,079
Accounts payable	303,885	237,673	252,527
Contract liabilities	91,864	0	0
Billings in excess of costs and estimated earnings	0	135,146	114,180
Accrued expenses and other current liabilities	$ 293,959	$ 236,407	$ 231,048
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	45,688,582	39,871,314	39,837,295
Common Stock, Shares, Outstanding	45,688,582	39,871,314	39,837,295
Consolidated Construction Joint Venture [Member] | Joint Venture Consolidated [Member]
Cash and cash equivalents	$ 82,047	$ 94,359	$ 80,195
Receivables, Net	38,828	52,031	42,099
Contract assets	24,479	0	0
Costs and estimated earnings in excess of billings	0	1,437	3,124
Other current assets	12,421	10,384	7,190
Property and equipment, net	38,854	38,361	28,398
Accounts payable	35,375	34,795	24,976
Contract liabilities	40,678	0	0
Billings in excess of costs and estimated earnings	0	37,701	32,657
Accrued expenses and other current liabilities	$ 2,147	$ 2,126	$ 1,156