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		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Guaranteed Minimum Benefits [Line Items]
Net premiums earned	$ 4,665	$ 4,490	$ 11,829	$ 11,556
Policy benefits and other reserve adjustments	130	83	379	282
Net realized gains (losses)	(60)	(760)	(194)	(878)
Guaranteed Minimum Death Benefit [Member]
Guaranteed Minimum Benefits [Line Items]
Net premiums earned	20	24	64	75
Policy benefits and other reserve adjustments	22	20	61	63
Guaranteed Minimum Income Benefit [Member]
Guaranteed Minimum Benefits [Line Items]
Net premiums earned	40	40	121	122
Policy benefits and other reserve adjustments	7	7	30	19
Net realized gains (losses)	75	(952)	41	(969)
(Loss) gain recognized in income	108	(919)	132	(866)
Net cash received	35	40	114	121
Net (increase) decrease in liability	$ 73	$ (959)	$ 18	$ (987)