Segment Information (details) - Assets by Segment (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Assets by segment
Total assets	$ 103,078	$ 103,812
Reportable Segments [Member]
Assets by segment
Total assets	102,632	103,307
Reportable Segments [Member] | Business and International Insurance [Member]
Assets by segment
Total assets	82,309	82,789
Reportable Segments [Member] | Bond & Specialty Insurance [Member]
Assets by segment
Total assets	7,525	7,648
Reportable Segments [Member] | Personal Insurance [Member]
Assets by segment
Total assets	12,798	12,870
Other assets [Member]
Assets by segment
Total assets	$ 446	$ 505