Fair Value Of Financial Instruments (Realized And Unrealized Gains And Losses Included In Earnings Pertaining To Level 3 Assets And Liabilities) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Unrealized gains (losses) on insured derivatives			$ 1,562	$ 1,473
Net gains (losses) on financial instruments at fair value and foreign exchange	5	7	62	(18)
Net investment losses related to other-than-temporary impairments	0	(8)	0	(105)
Fair Value Inputs Level 3 [Member] | Total Gains Losses Included In Earnings [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Net investment income	0	0	0	0
Unrealized gains (losses) on insured derivatives	285	(32)	1,562	1,473
Realized gains and other settlements on insured derivatives	(28)	12	(1,548)	(420)
Net gains (losses) on financial instruments at fair value and foreign exchange	(24)	(9)	(39)	(8)
Net investment losses related to other-than-temporary impairments	0	(7)	0	(67)
Total revenues	222	(101)	168	641
Fair Value Inputs Level 3 [Member] | Change In Unrealized Gains Losses For Period Included In Earnings For Assets And Liabilities Still Held [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Net investment income	0	0	0	0
Unrealized gains (losses) on insured derivatives	285	(33)	(301)	538
Realized gains and other settlements on insured derivatives	0	0	0	0
Net gains (losses) on financial instruments at fair value and foreign exchange	(1)	(16)	(11)	(8)
Net investment losses related to other-than-temporary impairments	0	0	0	0
Total revenues	278	(98)	(19)	276
Fair Value Inputs Level 3 [Member] | Variable Interest Entity Primary Beneficiary [Member] | Total Gains Losses Included In Earnings [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Net gains (losses) on financial instruments at fair value and foreign exchange	(11)	(65)	193	(337)
Fair Value Inputs Level 3 [Member] | Variable Interest Entity Primary Beneficiary [Member] | Change In Unrealized Gains Losses For Period Included In Earnings For Assets And Liabilities Still Held [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Net gains (losses) on financial instruments at fair value and foreign exchange	$ (6)	$ (49)	$ 293	$ (254)