Segment Reporting Revenue by Customer Type (details) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Revenue from External Customer [Line Items]
Revenues	$ 1,141.8	$ 974.9	$ 2,232.8	$ 1,881.9
Department of Defense and Intelligence Agencies
Revenue from External Customer [Line Items]
Revenues	159.3	141.6	292.9	284.9
Federal Civilian
Revenue from External Customer [Line Items]
Revenues	120.7	98.8	237.1	191.4
Other
Revenue from External Customer [Line Items]
Revenues	$ 11.2	$ 22.0	$ 19.3	$ 43.9