Assets and Liabilities Held for Sale Pretax Income (Tables) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Massachusetts Business
Assets and Liabilities Held for Sale Pretax Income [Line Items]
Disposal Group, Including Discontinued Operation, Operating Income (Loss)	$ (74.1)	$ (55.2)	$ (402.9)	$ 183.5

Amount of operating income (loss) attributable to disposal group, including, but not limited to, discontinued operation.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 5B
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109222650&loc=SL51721673-107760

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration