Income Taxes - Summary of Valuation Allowance (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Valuation Allowance [Roll Forward]
Balance at beginning of period	$ (103.0)	$ (139.0)	$ (133.0)
(Increase) decrease in valuation allowance	2.0	36.0	(6.0)
Balance at end of period	$ (101.0)	$ (103.0)	$ (139.0)

Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=65882285&loc=d3e32537-109319

Name:	us-gaap_DeferredTaxAssetsValuationAllowance
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant