Revenue Recognition - Schedule of Percentage of Sales by Contract and Customer (Details) - Sales Revenue, Net	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Contract | Fixed-price
Concentration Risk [Line Items]
Percentage of net sales	57.00%	60.00%	56.00%	61.00%
Contract | Cost-reimbursable
Concentration Risk [Line Items]
Percentage of net sales	43.00%	40.00%	44.00%	39.00%
Customers | U.S. government
Concentration Risk [Line Items]
Percentage of net sales	96.00%	96.00%	97.00%	96.00%
Customers | Non U.S. government
Concentration Risk [Line Items]
Percentage of net sales	4.00%	4.00%	3.00%	4.00%
Segment Concentration Risk | Real Estate Segment
Concentration Risk [Line Items]
Percentage of net sales	1.00%	1.00%	1.00%	1.00%