Variable Interest Entities (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Variable Interest Entity [Line Items]
Assets, current	$ 3,975,287		$ 3,975,287		$ 4,080,457
Liabilities, current	2,025,284		2,025,284		2,264,363
Revenue	$ 1,219,243	$ 1,276,427	$ 2,426,838	$ 2,527,156
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	$ 2,000		$ 2,000		600
Liabilities, current	1,900		1,900		500
VIEs
Variable Interest Entity [Line Items]
Assets, current	457,300		457,300		405,700
Liabilities, current	468,300		468,300		514,900
Assets, noncurrent	$ 5,600		$ 5,600		$ 14,200