Contingencies, Commitments and Guarantees (details) (USD $)	12 Months Ended
	Dec. 31, 2011 years count	Jan. 24, 2012	Jan. 19, 2012 count	Jul. 26, 2011	Dec. 31, 2010	Oct. 25, 2010 count
Contingencies and Commitments disclosure
Number of purported class action suits filed against TPC and other insurers in state court in West Virginia relative to asbestos direct action litigation	2
Maximum lump-sum payment included in the settlement reached in November 2003 relative to Statutory and Hawaii Actions	$ 412,000,000
Maximum payment required under May 2004 settlement resolving substantially all pending and similar future Common Law Claims relative to Statutory and Hawaii Actions	90,000,000
Number of putative class action lawsuits brought against a number of insurers relative to broker anti-trust litigation	4
Amount Company has agreed to pay under broker anti-trust litigation settlement	6,750,000
Number of other reinsurers beside American Re against which judgment was entered in a reinsurance dispute						3
Judgment amount awarded to Company in reinsurance dispute		251,000,000				251,000,000
Pre-judgment interest amount awarded to Company in reinsurance dispute						169,000,000
Total judgment amount awarded to Company in reinsurance dispute		467,000,000
Post-judgment interest amount accrued in reinsurance dispute		216,000,000
Post-judgment interest rate accruing on judgment against non-settling defendants	9.00%
Preliminary class settlement amount approved by court in workers' compensation matter, total				450,000,000
Number of parties who objected to the settlement and filed notices of appeal in workers' compensation matter			3
Preliminary class settlement amount approved by court in workers' compensation matter, anticipated allocation amount	90,000,000
Unfunded commitments to private equity limited partnerships and real estate partnerships	$ 1,150,000,000				$ 1,260,000,000
Period range for term of indemnification provisions arising from sales of business entities, minimum (in years)	7