Segment Reporting - Federal Government Segment Revenues by Customer Type (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Revenue from External Customer [Line Items]
Revenues	$ 4,581.1	$ 4,009.5	$ 3,502.1
Federal Government Business
Revenue from External Customer [Line Items]
Revenues	1,145.4	1,082.4	1,004.2
Federal Government Business | Department of Defense and Intelligence Agencies
Revenue from External Customer [Line Items]
Revenues	606.3	589.7	558.5
Federal Government Business | Federal Civilian
Revenue from External Customer [Line Items]
Revenues	503.4	421.8	370.6
Federal Government Business | Other
Revenue from External Customer [Line Items]
Revenues	$ 35.7	$ 70.9	$ 75.1