Income Taxes, Valuation Allowance (Details) $ in Millions	12 Months Ended
Dec. 31, 2017 USD ($)
Deferred Tax Assets Operating Loss Carryforwards Utilized or Expired [Member]
Valuation Allowance [Line Items]
Changes in valuation allowances for deferred tax assets	$ 8.0
Deferred Tax Assets Operating Loss Carryforwards Established or Continued [Member]
Valuation Allowance [Line Items]
Changes in valuation allowances for deferred tax assets	$ 12.1

Amount of increase (decrease) in the valuation allowance for a specified deferred tax asset.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 45
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=84176650&loc=d3e32123-109318

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