The portion of the valuation allowance pertaining to the deferred tax asset representing potential future taxable deductions from net operating loss carryforwards 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 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32559-109319

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 30
-Paragraph 5
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=75018887&loc=d3e30536-109315

Reference 3: 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=84230637&loc=d3e32537-109319

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

Income Taxes (Tax Examinations) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Jun. 30, 2016
Income Tax Examination [Line Items]
Increase in deferred tax assets	$ 137.1	$ 178.9
Tax Year 2012
Income Tax Examination [Line Items]
Increase in deferred tax assets			$ 0.6
Increase in valuation allowance			$ 0.6