Derivative Instruments (Credit Derivatives Sold) (Detail) (Insurance Operations [Member], USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Derivative [Line Items]
Total Notional Value of Credit Derivatives	$ 32,401	$ 53,014
Total Fair Value of Credit Derivatives	(1,655)	(2,934)
Credit Default Swap [Member]
Derivative [Line Items]
Weighted Average Remaining Expected Maturity	2 years 9 months 18 days	5 years 1 month 6 days
Total Notional Value of Credit Derivatives	26,826	47,002
Total Fair Value of Credit Derivatives	(1,641)	(2,858)
Insured Swaps [Member]
Derivative [Line Items]
Weighted Average Remaining Expected Maturity	19 years 2 months 12 days	19 years 4 months 24 days
Total Notional Value of Credit Derivatives	5,539	5,817
Total Fair Value of Credit Derivatives	(7)	(8)
Other Credit Derivatives [Member]
Derivative [Line Items]
Weighted Average Remaining Expected Maturity	28 years 6 months 0 days	1 year 9 months 18 days
Total Notional Value of Credit Derivatives	36	195
Total Fair Value of Credit Derivatives	(7)	(68)
Credit Rating Aaa [Member]
Derivative [Line Items]
Total Notional Value of Credit Derivatives	7,418	10,457
Total Fair Value of Credit Derivatives	(4)	(7)
Credit Rating Aaa [Member] | Credit Default Swap [Member]
Derivative [Line Items]
Total Notional Value of Credit Derivatives	7,418	10,457
Credit Rating Aaa [Member] | Insured Swaps [Member]
Derivative [Line Items]
Total Notional Value of Credit Derivatives	0	0
Credit Rating Aaa [Member] | Other Credit Derivatives [Member]
Derivative [Line Items]
Total Notional Value of Credit Derivatives	0	0
Credit Rating Aa [Member]
Derivative [Line Items]
Total Notional Value of Credit Derivatives	3,301	5,965
Total Fair Value of Credit Derivatives	0	(70)
Credit Rating Aa [Member] | Credit Default Swap [Member]
Derivative [Line Items]
Total Notional Value of Credit Derivatives	3,217	5,862
Credit Rating Aa [Member] | Insured Swaps [Member]
Derivative [Line Items]
Total Notional Value of Credit Derivatives	84	103
Credit Rating Aa [Member] | Other Credit Derivatives [Member]
Derivative [Line Items]
Total Notional Value of Credit Derivatives	0	0
Credit Rating A [Member]
Derivative [Line Items]
Total Notional Value of Credit Derivatives	6,522	8,914
Total Fair Value of Credit Derivatives	(6)	(72)
Credit Rating A [Member] | Credit Default Swap [Member]
Derivative [Line Items]
Total Notional Value of Credit Derivatives	2,856	5,253
Credit Rating A [Member] | Insured Swaps [Member]
Derivative [Line Items]
Total Notional Value of Credit Derivatives	3,666	3,661
Credit Rating A [Member] | Other Credit Derivatives [Member]
Derivative [Line Items]
Total Notional Value of Credit Derivatives	0	0
Credit Rating Bbb [Member]
Derivative [Line Items]
Total Notional Value of Credit Derivatives	8,929	13,553
Total Fair Value of Credit Derivatives	(603)	(732)
Credit Rating Bbb [Member] | Credit Default Swap [Member]
Derivative [Line Items]
Total Notional Value of Credit Derivatives	7,140	11,571
Credit Rating Bbb [Member] | Insured Swaps [Member]
Derivative [Line Items]
Total Notional Value of Credit Derivatives	1,789	1,982
Credit Rating Bbb [Member] | Other Credit Derivatives [Member]
Derivative [Line Items]
Total Notional Value of Credit Derivatives	0	0
Credit Rating Below Investment Grade [Member]
Derivative [Line Items]
Total Notional Value of Credit Derivatives	6,231	14,125
Total Fair Value of Credit Derivatives	(1,042)	(2,053)
Credit Rating Below Investment Grade [Member] | Credit Default Swap [Member]
Derivative [Line Items]
Total Notional Value of Credit Derivatives	6,195	13,859
Credit Rating Below Investment Grade [Member] | Insured Swaps [Member]
Derivative [Line Items]
Total Notional Value of Credit Derivatives	0	71
Credit Rating Below Investment Grade [Member] | Other Credit Derivatives [Member]
Derivative [Line Items]
Total Notional Value of Credit Derivatives	$ 36	$ 195