Insurance Claim Reserves (details) - Prior Year Reserve Development by Segment (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Prior year reserve development by segment
Net favorable prior year reserve development impacting the Company's results of operations	$ 715	$ 1,250	$ 1,330
Business Insurance [Member]
Prior year reserve development by segment
Net favorable prior year reserve development impacting the Company's results of operations	245	901	1,030
Financial, Professional & International Insurance [Member]
Prior year reserve development by segment
Net favorable prior year reserve development impacting the Company's results of operations	360	259	168
Personal Insurance [Member]
Prior year reserve development by segment
Net favorable prior year reserve development impacting the Company's results of operations	$ 110	$ 87	$ 135