Schedule II - Condensed Financial Information of Parent - Income Taxes (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Schedule of Deferred Tax Assets and Liabilities [Line Items]
Deferred income taxes	$ 781.0	$ 1,570.0
Parent Issuer
Schedule of Deferred Tax Assets and Liabilities [Line Items]
Deferred income taxes	$ 406.0	$ 527.0

Amount, after allocation of valuation allowances and deferred tax liability, of deferred tax asset attributable to deductible differences and carryforwards, with jurisdictional netting.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32537-109319

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