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, unless otherwise specified	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, 2014	Dec. 31, 2013	Dec. 31, 2012
Guaranteed Minimum Benefits [Line Items]
Net premiums earned	$ 4,370	$ 4,754	$ 4,332	$ 3,970	$ 4,363	$ 4,610	$ 4,067	$ 3,573	$ 17,426	$ 16,613	$ 15,677
Policy benefits and other reserve adjustments	134	125	144	114	136	138	110	131	517	515	521
Net realized gains (losses) including OTTI	(210)	(120)	(73)	(104)	154	40	104	206	(507)	504	78
GMDB
Guaranteed Minimum Benefits [Line Items]
Net premiums earned									71	77	85
Policy benefits and other reserve adjustments									50	73	60
GLB
Guaranteed Minimum Benefits [Line Items]
Net premiums earned									138	149	160
Policy benefits and other reserve adjustments									36	27	61
Net realized gains (losses) including OTTI									(213)	929	203
Gain (loss) recognized in income									(111)	1,051	302
Net cash received									125	126	149
Net (increase) decrease in liability									$ (236)	$ 925	$ 153