Discontinued Operations (Details) - USD ($) $ in Millions		3 Months Ended	6 Months Ended
Mar. 13, 2020	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash purchase price				$ 1,159.4	$ 0.0
Income (loss):
Income (loss) from discontinued operations, net of tax		$ (2.1)	$ 25.5	1,066.4	38.8
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
Revenue		0.0	184.4	149.5	325.7
Income (loss):
Operations		0.1	34.0	9.1	51.7
Gain on sale		(0.9)	0.0	1,060.8	0.0
Income from discontinued operations		(0.8)	34.0	1,069.9	51.7
Income tax provision		1.3	8.5	3.5	12.9
Income (loss) from discontinued operations, net of tax		$ (2.1)	$ 25.5	$ 1,066.4	$ 38.8

Amount before tax of gain (loss) not previously recognized resulting from the disposal of a discontinued operation.

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