Income Taxes - Components of Income Tax Expense (Benefit) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Current	$ 128.7	$ 18.8	$ (18.3)
Deferred	(26.8)	(48.0)	(153.2)
Income tax benefit related to continuing operations	$ 101.9	$ (29.2)	$ (171.5)

Amount of deferred federal income tax expense (benefit) pertaining to income (loss) from continuing operations.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
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-URI http://asc.fasb.org/extlink&oid=34349781&loc=d3e330036-122817

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration