Basis of Presentation and Significant Accounting Policies Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income (Details) $ in Thousands	Dec. 31, 2017 USD ($)
Cumulative effect of adoption of new accounting principles	$ 0
Cumulative Earnings
Cumulative effect of adoption of new accounting principles	$ (9,943)

Amount after tax of increase (decrease) to equity or (increase) decrease to net assets, resulting from the cumulative effect adjustment of a new accounting principle applied in the period of adoption.

No definition available.

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