Claim and Claim Adjustment Expense Reserves Net prior year claim and allocated claim adjustment expense reserve development for International segment (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Pretax (favorable) unfavorable net prior year claim and allocated claim adjustment expense reserve development, excluding Life & Group	$ (52)	$ (7)
International [Member]
Medical Professional Liability	0	0
Other Professional Liability	(1)	0
Liability	0	(5)
Property & Marine	(4)	(6)
Other	1	7
Pretax (favorable) unfavorable net prior year claim and allocated claim adjustment expense reserve development, excluding Life & Group	$ (4)	$ (4)