Accumulated Other Comprehensive Income/(Loss) (Narrative) (Details) - ASU 2016-01 $ in Millions	Dec. 31, 2017 USD ($)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative-effect adjustment	$ 67.9
Retained earnings
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative-effect adjustment	$ 67.9

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