Derivative Instruments (Credit Derivatives Sold) (Detail) (Insurance Operations [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Derivative [Line Items]
Derivative notional amount	$ 13,525invest_DerivativeNotionalAmount	$ 28,935invest_DerivativeNotionalAmount
Total fair value of credit derivatives	(246)	(1,152)
Credit Default Swap [Member]
Derivative [Line Items]
Weighted average remaining expected maturity	1 year 7 months 6 days	2 years 7 months 6 days
Derivative notional amount	9,481	23,954
Total fair value of credit derivatives	(244)	(1,132)
Insured Swaps [Member]
Derivative [Line Items]
Weighted average remaining expected maturity	16 years 8 months 12 days	18 years 6 months 0 days
Derivative notional amount	4,044	4,945
Total fair value of credit derivatives	(2)	(5)
Other Credit Derivatives [Member]
Derivative [Line Items]
Weighted average remaining expected maturity		28 years 0 months 0 days
Derivative notional amount	0	36
Total fair value of credit derivatives	0	(15)
Credit Rating Aaa [Member]
Derivative [Line Items]
Derivative notional amount	6,914	7,406
Total fair value of credit derivatives	(2)	(2)
Credit Rating Aaa [Member] \| Credit Default Swap [Member]
Derivative [Line Items]
Derivative notional amount	6,914	7,406
Credit Rating Aaa [Member] \| Insured Swaps [Member]
Derivative [Line Items]
Derivative notional amount	0	0
Credit Rating Aaa [Member] \| Other Credit Derivatives [Member]
Derivative [Line Items]
Derivative notional amount	0	0
Credit Rating Aa [Member]
Derivative [Line Items]
Derivative notional amount	363	2,049
Total fair value of credit derivatives	0	0
Credit Rating Aa [Member] \| Credit Default Swap [Member]
Derivative [Line Items]
Derivative notional amount	246	1,972
Credit Rating Aa [Member] \| Insured Swaps [Member]
Derivative [Line Items]
Derivative notional amount	117	77
Credit Rating Aa [Member] \| Other Credit Derivatives [Member]
Derivative [Line Items]
Derivative notional amount	0	0
Credit Rating A [Member]
Derivative [Line Items]
Derivative notional amount	3,903	4,350
Total fair value of credit derivatives	(2)	(3)
Credit Rating A [Member] \| Credit Default Swap [Member]
Derivative [Line Items]
Derivative notional amount	968	1,068
Credit Rating A [Member] \| Insured Swaps [Member]
Derivative [Line Items]
Derivative notional amount	2,935	3,282
Credit Rating A [Member] \| Other Credit Derivatives [Member]
Derivative [Line Items]
Derivative notional amount	0	0
Credit Rating Bbb [Member]
Derivative [Line Items]
Derivative notional amount	1,163	9,138
Total fair value of credit derivatives	(2)	(78)
Credit Rating Bbb [Member] \| Credit Default Swap [Member]
Derivative [Line Items]
Derivative notional amount	193	7,552
Credit Rating Bbb [Member] \| Insured Swaps [Member]
Derivative [Line Items]
Derivative notional amount	970	1,586
Credit Rating Bbb [Member] \| Other Credit Derivatives [Member]
Derivative [Line Items]
Derivative notional amount	0	0
Credit Rating Below Investment Grade [Member]
Derivative [Line Items]
Derivative notional amount	1,182	5,992
Total fair value of credit derivatives	(240)	(1,069)
Credit Rating Below Investment Grade [Member] \| Credit Default Swap [Member]
Derivative [Line Items]
Derivative notional amount	1,160	5,956
Credit Rating Below Investment Grade [Member] \| Insured Swaps [Member]
Derivative [Line Items]
Derivative notional amount	22	0
Credit Rating Below Investment Grade [Member] \| Other Credit Derivatives [Member]
Derivative [Line Items]
Derivative notional amount	$ 0	$ 36

Derivative Instruments (Credit Derivatives Sold) (Detail) (Insurance Operations [Member], USD $)
In Millions, unless otherwise specified

12 Months Ended

Dec. 31, 2014

Dec. 31, 2013

Derivative [Line Items]

Derivative notional amount

$ 13,525

$ 28,935

Total fair value of credit derivatives

(246)

(1,152)

Credit Default Swap [Member]