Derivative Instruments - Asset and Liability Management Derivative Positions of Company (Detail) - Asset and Liability Management Positions [Member] - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Derivative [Line Items]
Notional Value, Assets	$ 25,233	$ 20,217
Fair Value, Assets	294	215
Notional Value, Liabilities	20,511	21,623
Fair Value, Liabilities	375	472
Other Derivatives [Member]
Derivative [Line Items]
Notional Value, Assets	111	58
Fair Value, Assets	$ 1	$ 4
Derivative Asset Average Remaining Maturity Period	7 days	11 days
Notional Value, Liabilities	$ 682	$ 390
Fair Value, Liabilities	$ 63	$ 48
Derivative Liability Average Remaining Maturity Period	2 years 6 months 7 days	3 years 2 months 12 days
Fair Value Hedges [Member] | Interest Rate Contracts [Member] | Receive Fixed/Pay Floating Swaps [Member]
Derivative [Line Items]
Notional Value, Assets	$ 3,050	$ 2,750
Fair Value, Assets	$ 104	$ 65
Derivative Asset Average Remaining Maturity Period	4 years 8 months 5 days	5 years 8 months 9 days
Cash Flow Hedges [Member] | Interest Rate Contracts [Member] | Receive Fixed/Pay Floating Swaps [Member]
Derivative [Line Items]
Notional Value, Assets		$ 250
Derivative Asset Average Remaining Maturity Period		1 month 28 days
Cash Flow Hedges [Member] | Interest Rate Contracts [Member] | Pay Fixed/Receive Floating Swaps [Member]
Derivative [Line Items]
Notional Value, Assets	$ 32	$ 272
Fair Value, Assets		$ 6
Derivative Asset Average Remaining Maturity Period	7 years 1 month 17 days	7 years 9 months 4 days
Notional Value, Liabilities	$ 6,915	$ 5,748
Fair Value, Liabilities	$ 222	$ 315
Derivative Liability Average Remaining Maturity Period	3 years 4 months 24 days	1 year 11 months 9 days
Net Investment Hedges [Member] | Foreign Exchange Forward Contracts [Member]
Derivative [Line Items]
Notional Value, Assets	$ 1,015	$ 1,047
Fair Value, Assets	$ 8	$ 31
Derivative Asset Average Remaining Maturity Period	15 days	15 days
Other Economic Hedges [Member] | Interest Rate Contracts [Member] | Receive Fixed/Pay Floating Swaps [Member]
Derivative [Line Items]
Notional Value, Assets	$ 3,962	$ 3,552
Fair Value, Assets	$ 79	$ 14
Derivative Asset Average Remaining Maturity Period	10 years 2 months 19 days	10 years 2 months 19 days
Notional Value, Liabilities		$ 250
Fair Value, Liabilities		$ 1
Derivative Liability Average Remaining Maturity Period		10 years 2 months 19 days
Other Economic Hedges [Member] | Interest Rate Contracts [Member] | Pay Fixed/Receive Floating Swaps [Member]
Derivative [Line Items]
Notional Value, Assets		$ 15
Derivative Asset Average Remaining Maturity Period		10 years 2 months 19 days
Notional Value, Liabilities	$ 77
Fair Value, Liabilities	$ 2
Derivative Liability Average Remaining Maturity Period	9 years 5 months 12 days
Other Economic Hedges [Member] | Interest Rate Contracts [Member] | Futures and Forwards [Member] | Purchased [Member]
Derivative [Line Items]
Notional Value, Assets	$ 6,045	$ 4,839
Fair Value, Assets	$ 48	$ 45
Derivative Asset Average Remaining Maturity Period	1 month 10 days	26 days
Notional Value, Liabilities	$ 51	$ 60
Fair Value, Liabilities	$ 1
Derivative Liability Average Remaining Maturity Period	18 days	29 days
Other Economic Hedges [Member] | Interest Rate Contracts [Member] | Futures and Forwards [Member] | Written [Member]
Derivative [Line Items]
Notional Value, Assets	$ 694	$ 448
Fair Value, Assets	$ 5	$ 10
Derivative Asset Average Remaining Maturity Period	1 year 7 months 21 days	1 month 17 days
Notional Value, Liabilities	$ 6,618	$ 6,713
Fair Value, Liabilities	$ 66	$ 62
Derivative Liability Average Remaining Maturity Period	1 month 10 days	1 month 2 days
Other Economic Hedges [Member] | Interest Rate Contracts [Member] | Options [Member] | Purchased [Member]
Derivative [Line Items]
Notional Value, Assets	$ 3,075	$ 2,500
Derivative Asset Average Remaining Maturity Period	26 days	22 days
Other Economic Hedges [Member] | Interest Rate Contracts [Member] | Options [Member] | Written [Member]
Derivative [Line Items]
Notional Value, Assets	$ 2,377	$ 2,643
Fair Value, Assets	$ 38	$ 31
Derivative Asset Average Remaining Maturity Period	1 month 2 days	29 days
Notional Value, Liabilities	$ 8	$ 4
Fair Value, Liabilities	$ 1
Derivative Liability Average Remaining Maturity Period	29 days	1 month 10 days
Other Economic Hedges [Member] | Foreign Exchange Forward Contracts [Member]
Derivative [Line Items]
Notional Value, Assets	$ 3,673	$ 510
Fair Value, Assets	$ 9	$ 3
Derivative Asset Average Remaining Maturity Period	4 days	11 days
Notional Value, Liabilities	$ 3,240	$ 6,176
Fair Value, Liabilities	$ 14	$ 41
Derivative Liability Average Remaining Maturity Period	11 days	7 days
Other Economic Hedges [Member] | Equity Contracts [Member]
Derivative [Line Items]
Notional Value, Assets		$ 86
Fair Value, Assets		$ 3
Derivative Asset Average Remaining Maturity Period		7 months 6 days
Notional Value, Liabilities	$ 87
Fair Value, Liabilities	$ 2
Derivative Liability Average Remaining Maturity Period	6 months 15 days
Other Economic Hedges [Member] | Credit Contracts [Member]
Derivative [Line Items]
Notional Value, Assets	$ 1,199	$ 1,247
Fair Value, Assets	$ 2	$ 3
Derivative Asset Average Remaining Maturity Period	2 years 5 months 9 days	3 years 3 months 15 days
Notional Value, Liabilities	$ 2,833	$ 2,282
Fair Value, Liabilities	$ 4	$ 5
Derivative Liability Average Remaining Maturity Period	2 years 10 months 10 days	2 years 10 months 6 days