Revenue from Contract with Customers Revenue by Contractor Type (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Revenue by Contract Type [Line Items]
Revenues	$ 2,553,956	$ 2,518,384	$ 2,222,559
Prime contractor
Revenue by Contract Type [Line Items]
Revenues	2,376,018	2,297,452	1,995,471
Subcontractor
Revenue by Contract Type [Line Items]
Revenues	$ 177,938	$ 220,932	$ 227,088