Variable Interest Entities (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Variable Interest Entity [Line Items]
Assets, current	$ 3,937,431		$ 3,937,431		$ 4,080,457
Liabilities, current	1,932,989		1,932,989		2,264,363
Revenue	$ 1,178,222	$ 1,442,091	$ 3,605,060	$ 3,969,247
Purple Line Extension Section 2 And Section 3
Variable Interest Entity [Line Items]
Percent interest in the joint venture			75.00%
Newark Airport Terminal One Design Build Project
Variable Interest Entity [Line Items]
Percent interest in the joint venture			80.00%
Joint Venture With O&G Industries | Purple Line Extension Section 2 And Section 3
Variable Interest Entity [Line Items]
Revenue			$ 2,800,000
O&G | Purple Line Extension Section 2 And Section 3
Variable Interest Entity [Line Items]
Noncontrolling interest, ownership percentage by noncontrolling owners	25.00%		25.00%
Joint Venture With Parsons | Newark Airport Terminal One Design Build Project
Variable Interest Entity [Line Items]
Revenue			$ 1,400,000
Parsons Corporation | Newark Airport Terminal One Design Build Project
Variable Interest Entity [Line Items]
Noncontrolling interest, ownership percentage by noncontrolling owners	20.00%		20.00%
Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Assets, current	$ 1,700		$ 1,700		600
Liabilities, current	1,500		1,500		500
VIEs
Variable Interest Entity [Line Items]
Assets, current	510,100		510,100		405,700
Liabilities, current	460,800		460,800		514,900
Assets, noncurrent	$ 3,300		$ 3,300		$ 14,200