Claim and Claim Adjustment Expense Reserves Net prior year claim and allocated claim adjustment expense reserve development for International segment (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Pretax (favorable) unfavorable net prior year claim and allocated claim adjustment expense reserve development, excluding Life & Group	$ (7)	$ 25
International [Member]
Medical Professional Liability	0	1
Other Professional Liability	0	(1)
Liability	(5)	(2)
Property & Marine	(6)	8
Other	7	(6)
Commutations	0	10
Pretax (favorable) unfavorable net prior year claim and allocated claim adjustment expense reserve development, excluding Life & Group	$ (4)	$ 10