Income Taxes Income Taxes (Narrative) (Details) $ in Millions	12 Months Ended
Dec. 31, 2017 USD ($)
Income Tax Disclosure [Abstract]
Discrete income tax benefit	$ 3.1

Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Change in Tax Rate, Provisional Income Tax Expense (Benefit)

No definition available.

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Balance Type:	debit
Period Type:	duration