Discontinued Operations (Details) - USD ($) $ in Millions		3 Months Ended
	Mar. 13, 2020	Mar. 31, 2021	Mar. 31, 2020
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash purchase price		$ 0.0	$ 1,164.7
Income
Income from discontinued operations, net of tax		$ 0.0	1,068.5
U.S. Federal Business | Discontinued Operations, Disposed of by Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash purchase price	$ 1,200.0
Net cash proceeds of the sale (net of working capital adjustments and transaction costs)	$ 1,164.7
Revenue			149.5
Income
Operations			9.0
Gain on sale			1,061.7
Income from discontinued operations			1,070.7
Income tax provision			2.2
Income from discontinued operations, net of tax			$ 1,068.5