Segment Reporting Revenue by Customer Type (details) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Revenue from External Customer [Line Items]
Revenues	$ 1,091.0	$ 907.0
Department of Defense and Intelligence Agencies
Revenue from External Customer [Line Items]
Revenues	133.6	143.3
Federal Civilian
Revenue from External Customer [Line Items]
Revenues	116.4	92.5
Other
Revenue from External Customer [Line Items]
Revenues	$ 8.1	$ 22.0