CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Cash and cash equivalents	$ 200,263	$ 272,804	$ 193,581
Receivables, Net	368,215	473,246	330,192
Contract assets	260,250	219,754	178,663
Other current assets	54,590	48,731	43,125
Property and equipment, net	552,504	549,688	409,708
Accounts payable	216,966	251,481	226,253
Contract liabilities	90,752	105,449	71,030
Accrued expenses and other current liabilities	$ 265,102	$ 273,626	$ 233,637
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	46,812,366	46,665,889	40,047,187
Common Stock, Shares, Outstanding	46,812,366	46,665,889	40,047,187
Equity Method Investee [Member] | Construction [Member]
Cash and cash equivalents	$ 131,481	$ 131,965	$ 91,903
Receivables, Net	24,990	21,237	17,598
Contract assets	15,140	19,699	23,889
Other current assets	11,795	11,744	14,180
Property and equipment, net	35,377	34,761	44,655
Accounts payable	41,013	37,086	31,854
Contract liabilities	46,775	60,288	33,760
Accrued expenses and other current liabilities	$ 3,269	$ 2,046	$ 2,090