Basis of Presentation and Accounting Policies (details)	9 Months Ended
Sep. 30, 2012 item
Basis of Presentation and Accounting Policies disclosure
Number of reportable business segments	3
Number of groups comprising Business Insurance Core	6

Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

No definition available.

Name:	us-gaap_NumberOfReportableSegments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration