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Quarterly Financial Data (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended						12 Months Ended			28 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2020
Quarterly Financial Data [Line Items]
Disposal Group, Not Discontinued Operation, Loss (Gain) on Write-down							$ 412.4
Proceeds From Insurance Settlement					$ 297.0	$ 108.0				$ 800.0
Loss on early extinguishment of long-term debt	$ 243.4						$ (243.5)	$ 0.0	$ (45.5)
Columbia Of Massachusetts
Quarterly Financial Data [Line Items]
Disposal Group, Not Discontinued Operation, Loss (Gain) on Write-down		$ 84.4	$ 280.2
Goodwill, Impairment Loss				$ 204.8
Impairment of Intangible Assets, Finite-lived				$ 209.7

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Amount, before tax, of (gain) loss recognized for the (reversal of write-down) write-down to fair value, less cost to sell, of a disposal group. Excludes discontinued operations.

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