Summary of Significant Accounting Policies - Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended
Sep. 30, 2016	Jun. 30, 2016	Sep. 30, 2017
Income Taxes
Reversal of valuation allowance included in income tax benefit	$ 4.3	$ 112.9
Unrecognized tax benefits			$ 0.0

Amount of income tax expense (benefit) from continuing operations attributable to an adjustment of a deferred tax liability or asset for enacted changes in tax laws or rates or a change in the tax status of the entity.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 9
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=65882285&loc=d3e32639-109319

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