Variable Interest Entities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Variable Interest Entity [Line Items]
Assets, current	$ 3,998,077		$ 4,080,457
Liabilities, current	2,131,059		2,264,363
Revenue	$ 1,207,595	$ 1,250,729
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%
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%
Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Assets, current	$ 900		600
Liabilities, current	800		500
VIEs
Variable Interest Entity [Line Items]
Assets, current	404,200		405,700
Liabilities, current	449,300		514,900
Assets, noncurrent	$ 9,700		$ 14,200