Income Taxes (Details) $ in Millions	6 Months Ended
Jun. 30, 2017 USD ($)
Income Tax Disclosure [Abstract]
Expected refund in 2017	$ 9.0
Expected refunds in future periods	11.0
Tax benefit due to release of a portion of valuation allowance previously offsetting deferred tax assets associated with existing AMT credit carryforwards	$ 20.0

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