Segment Reporting Revenue by Customer Type (details) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Revenue from External Customer [Line Items]
Revenues	$ 1,049.0	$ 1,128.8
Department of Defense and Intelligence Agencies
Revenue from External Customer [Line Items]
Revenues	150.1	132.9
Federal Civilian
Revenue from External Customer [Line Items]
Revenues	157.8	153.1
Other
Revenue from External Customer [Line Items]
Revenues	$ 9.6	$ 10.7