Segment Reporting Revenue by Customer Type (details) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Revenue from External Customer [Line Items]
Revenues	$ 1,128.8	$ 1,091.0
Department of Defense and Intelligence Agencies
Revenue from External Customer [Line Items]
Revenues	132.9	133.6
Federal Civilian
Revenue from External Customer [Line Items]
Revenues	153.1	116.4
Other
Revenue from External Customer [Line Items]
Revenues	$ 10.7	$ 8.1