Segment Information (details) - Assets by Segment (USD $) In Millions	Jun. 30, 2011	Dec. 31, 2010
Assets by segment
Total assets	$ 106,468	$ 105,656
Total reportable segments
Assets by segment
Total assets	105,681	105,049
Business Insurance
Assets by segment
Total assets	78,330	78,165
Financial, Professional & International Insurance
Assets by segment
Total assets	13,840	13,461
Personal Insurance
Assets by segment
Total assets	13,511	13,423
Other
Assets by segment
Total assets	$ 787	$ 607