Business Combinations, Goodwill and Intangible Assets, Goodwill (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Dec. 31, 2019	Jun. 30, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Goodwill [Roll Forward]
Goodwill, gross			$ 62.4	$ 37.2
Impairment of the carrying value of goodwill			(18.4)	(18.4)
Goodwill	$ 18.8		18.8	44.0	$ 18.8
Goodwill, acquired			0.0	25.2
Goodwill impairment	(25.2)	$ (18.4)	(25.2)	0.0	(18.4)
Goodwill, total increase			(25.2)	25.2
Goodwill, gross	62.4		62.4	62.4	37.2
Impairment of the carrying value of goodwill	$ (43.6)		$ (43.6)	$ (18.4)	$ (18.4)

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

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Amount before accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Amount of accumulated impairment loss for an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Amount of increase (decrease) of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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