Accounting Policies - Income Taxes (Details) $ in Thousands	12 Months Ended
Dec. 31, 2017 USD ($)
Accounting Policies [Abstract]
Reclass of Stranded Tax Effects from AOCI to Retained Earnings	$ 0

Reclass of Stranded Tax Effects from AOCI to Retained Earnings related to ASU 2018-02

No definition available.

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Period Type:	duration