Goodwill (details) - Goodwill by Segment (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Goodwill by segment
Goodwill	$ 3,365	$ 3,365
Reportable Segments [Member] | Business Insurance [Member]
Goodwill by segment
Goodwill	2,168	2,168
Reportable Segments [Member] | Financial, Professional & International Insurance [Member]
Goodwill by segment
Goodwill	557	557
Reportable Segments [Member] | Personal Insurance [Member]
Goodwill by segment
Goodwill	613	613
Other [Member]
Goodwill by segment
Goodwill	$ 27	$ 27