Derivative Instruments (Credit Derivatives Sold) (Detail) (Insurance Operations [Member], USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Derivative [Line Items]
Total Notional Value of Credit Derivatives	$ 53,014	$ 73,551
Total Fair Value of Credit Derivatives	(2,934)	(5,343)
Insured Credit Default Swaps [Member]
Derivative [Line Items]
Weighted Average Remaining Expected Maturity	5.1 Years	5.6 Years
Total Notional Value of Credit Derivatives	47,002	65,557
Total Fair Value of Credit Derivatives	(2,858)	(4,716)
Non-Insured Credit Default Swaps-VIE [Member]
Derivative [Line Items]
Weighted Average Remaining Expected Maturity		3.6 Years
Total Notional Value of Credit Derivatives		643
Total Fair Value of Credit Derivatives		(527)
Insured Swaps [Member]
Derivative [Line Items]
Weighted Average Remaining Expected Maturity	19.4 Years	19.7 Years
Total Notional Value of Credit Derivatives	5,817	7,156
Total Fair Value of Credit Derivatives	(8)	(9)
All Other [Member]
Derivative [Line Items]
Weighted Average Remaining Expected Maturity	1.8 Years	2.8 Years
Total Notional Value of Credit Derivatives	195	195
Total Fair Value of Credit Derivatives	(68)	(91)
AAA [Member]
Derivative [Line Items]
Total Notional Value of Credit Derivatives	10,457	15,475
Total Fair Value of Credit Derivatives	(7)	(114)
AAA [Member] | Insured Credit Default Swaps [Member]
Derivative [Line Items]
Total Notional Value of Credit Derivatives	10,457	15,475
AA [Member]
Derivative [Line Items]
Total Notional Value of Credit Derivatives	5,965	12,229
Total Fair Value of Credit Derivatives	(70)	(116)
AA [Member] | Insured Credit Default Swaps [Member]
Derivative [Line Items]
Total Notional Value of Credit Derivatives	5,862	12,065
AA [Member] | Insured Swaps [Member]
Derivative [Line Items]
Total Notional Value of Credit Derivatives	103	164
A [Member]
Derivative [Line Items]
Total Notional Value of Credit Derivatives	8,914	10,606
Total Fair Value of Credit Derivatives	(72)	(205)
A [Member] | Insured Credit Default Swaps [Member]
Derivative [Line Items]
Total Notional Value of Credit Derivatives	5,253	6,336
A [Member] | Insured Swaps [Member]
Derivative [Line Items]
Total Notional Value of Credit Derivatives	3,661	4,270
BBB [Member]
Derivative [Line Items]
Total Notional Value of Credit Derivatives	13,553	16,631
Total Fair Value of Credit Derivatives	(732)	(1,355)
BBB [Member] | Insured Credit Default Swaps [Member]
Derivative [Line Items]
Total Notional Value of Credit Derivatives	11,571	14,042
BBB [Member] | Insured Swaps [Member]
Derivative [Line Items]
Total Notional Value of Credit Derivatives	1,982	2,589
Below Investment Grade [Member]
Derivative [Line Items]
Total Notional Value of Credit Derivatives	14,125	18,610
Total Fair Value of Credit Derivatives	(2,053)	(3,553)
Below Investment Grade [Member] | Insured Credit Default Swaps [Member]
Derivative [Line Items]
Total Notional Value of Credit Derivatives	13,859	17,639
Below Investment Grade [Member] | Non-Insured Credit Default Swaps-VIE [Member]
Derivative [Line Items]
Total Notional Value of Credit Derivatives		643
Below Investment Grade [Member] | Insured Swaps [Member]
Derivative [Line Items]
Total Notional Value of Credit Derivatives	71	133
Below Investment Grade [Member] | All Other [Member]
Derivative [Line Items]
Total Notional Value of Credit Derivatives	$ 195	$ 195