Reinsurance Reinsurance (Assumed Life Reinsurance Programs Involving Minimum Benefit Guarantees Under Annuity Contracts - Schedule Of Guaranteed Minimum Benefits Income And Expense) (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Guaranteed Minimum Benefits [Line Items]
Net premiums earned	$ 4,207	$ 4,719	$ 4,360	$ 3,927	$ 4,370	$ 4,754	$ 4,332	$ 3,970	$ 17,213	$ 17,426	$ 16,613
Policy benefits and other reserve adjustments	159	89	153	142	134	125	144	114	543	517	515
Net realized gains (losses) including OTTI	$ (60)	$ (397)	$ 126	$ (89)	$ (210)	$ (120)	$ (73)	$ (104)	(420)	(507)	504
GMDB
Guaranteed Minimum Benefits [Line Items]
Net premiums earned									61	71	77
Policy benefits and other reserve adjustments									34	50	73
GLB
Guaranteed Minimum Benefits [Line Items]
Net premiums earned									121	138	149
Policy benefits and other reserve adjustments									45	36	27
Net realized gains (losses) including OTTI									(203)	(213)	929
Gain (loss) recognized in income									(127)	(111)	1,051
Net cash received									98	125	126
Net (increase) decrease in liability									$ (225)	$ (236)	$ 925