Statutory Financial Information (Narrative) (Details) $ in Millions	Dec. 31, 2015 USD ($)
Statutory Accounting Practices [Line Items]
Amount of cash and investments held as funds at Lloyd's	$ 827.9
United States [Member]
Statutory Accounting Practices [Line Items]
Amount available for dividend payment	354.0
Bermuda [Member]
Statutory Accounting Practices [Line Items]
Amount available for dividend payment	$ 491.5

Amount of dividends available for payment after computation of statutory restrictions on capital surplus.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(e))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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