Investment Income And Gains And Losses (Total Investment Income From All Operations) (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
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net investment income	$ 67		$ 109		$ 223		$ 352
Total net realized gains (losses)	28	[1]	(11)	[1]	(106)	[1]	(8)	[1]
Total investment income	95		98		117		344
Fixed-Maturity Investments [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net investment income	47		88		160		284
Gains	42		46		94		117
Losses	(12)		(56)		(190)		(133)
Total net realized gains (losses)	30		(10)		(96)		(16)
Short-Term Investments [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net investment income	1		1		5		5
Other Investments [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net investment income	2		3		7		10
Gains					6		9
Losses	(2)		(1)		(16)		(1)
Total net realized gains (losses)	(2)		(1)		(10)		8
Variable Interest Entity [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net investment income	$ 17		$ 17		$ 51		$ 53

[1] These balances are included in the "Net gains (losses) on financial instruments at fair value and foreign exchange" and "Net investment losses related to other-than-temporary impairments" line items on the Company's consolidated statements of operations.