Segment Reporting Revenue by Customer Type (details) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Revenue from External Customer [Line Items]
Revenues	$ 1,130.9	$ 1,141.8	$ 2,259.7	$ 2,232.8
Department of Defense and Intelligence Agencies
Revenue from External Customer [Line Items]
Revenues	155.0	159.3	287.9	292.9
Federal Civilian
Revenue from External Customer [Line Items]
Revenues	155.7	120.7	308.8	237.1
Other
Revenue from External Customer [Line Items]
Revenues	$ 8.9	$ 11.2	$ 19.6	$ 19.3