Derivative Instruments - Asset and Liability Management Derivative Positions of Company (Detail) - Asset and Liability Management Positions [Member] - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Derivative [Line Items]
Notional Value, Assets	$ 31,943	$ 27,442
Fair Value, Assets	598	201
Notional Value, Liabilities	23,617	22,818
Fair Value, Liabilities	642	286
Other Derivatives [Member]
Derivative [Line Items]
Notional Value, Assets	597	$ 36
Fair Value, Assets	$ 9
Derivative Asset Average Remaining Maturity Period	7 days	15 days
Notional Value, Liabilities	$ 1,278	$ 662
Fair Value, Liabilities	$ 73	$ 64
Derivative Liability Average Remaining Maturity Period	1 year 4 months 2 days	2 years 7 months 6 days
Fair Value Hedges [Member] | Interest Rate Contracts [Member] | Receive Fixed/Pay Floating Swaps [Member]
Derivative [Line Items]
Notional Value, Assets	$ 2,550	$ 3,050
Fair Value, Assets	$ 128	$ 73
Derivative Asset Average Remaining Maturity Period	5 years 11 days	4 years 5 months 5 days
Cash Flow Hedges [Member] | Interest Rate Contracts [Member] | Pay Fixed/Receive Floating Swaps [Member]
Derivative [Line Items]
Notional Value, Assets	$ 1,500	$ 1,772
Fair Value, Assets	$ 6	$ 7
Derivative Asset Average Remaining Maturity Period	9 years 10 months 17 days	9 years 2 months 19 days
Notional Value, Liabilities	$ 6,439	$ 5,009
Fair Value, Liabilities	$ 193	$ 146
Derivative Liability Average Remaining Maturity Period	3 years 3 months 22 days	1 year 1 month 17 days
Net Investment Hedges [Member] | Foreign Exchange Forward Contracts [Member]
Derivative [Line Items]
Notional Value, Assets		$ 1,140
Fair Value, Assets		$ 4
Derivative Asset Average Remaining Maturity Period		15 days
Notional Value, Liabilities	$ 1,170
Fair Value, Liabilities	$ 30
Derivative Liability Average Remaining Maturity Period	15 days
Other Economic Hedges [Member] | Interest Rate Contracts [Member] | Receive Fixed/Pay Floating Swaps [Member]
Derivative [Line Items]
Notional Value, Assets	$ 9,656	$ 3,733
Fair Value, Assets	$ 290	$ 42
Derivative Asset Average Remaining Maturity Period	10 years	9 years 11 months 23 days
Notional Value, Liabilities		$ 4,748
Fair Value, Liabilities		$ 18
Derivative Liability Average Remaining Maturity Period		10 years 2 months 5 days
Other Economic Hedges [Member] | Interest Rate Contracts [Member] | Pay Fixed/Receive Floating Swaps [Member]
Derivative [Line Items]
Notional Value, Assets		$ 287
Fair Value, Assets		$ 2
Derivative Asset Average Remaining Maturity Period		9 years 9 months 26 days
Notional Value, Liabilities	$ 4,381	$ 4,158
Fair Value, Liabilities	$ 277	$ 35
Derivative Liability Average Remaining Maturity Period	9 years 8 months 16 days	9 years 11 months 19 days
Other Economic Hedges [Member] | Interest Rate Contracts [Member] | Futures and Forwards [Member] | Purchased [Member]
Derivative [Line Items]
Notional Value, Assets	$ 5,650	$ 3,812
Fair Value, Assets	$ 54	$ 17
Derivative Asset Average Remaining Maturity Period	29 days	26 days
Notional Value, Liabilities	$ 21	$ 452
Fair Value, Liabilities	$ 2	$ 1
Derivative Liability Average Remaining Maturity Period	18 days	22 days
Other Economic Hedges [Member] | Interest Rate Contracts [Member] | Futures and Forwards [Member] | Written [Member]
Derivative [Line Items]
Notional Value, Assets	$ 455	$ 3,201
Fair Value, Assets	$ 5	$ 12
Derivative Asset Average Remaining Maturity Period	2 months 1 day	1 month 2 days
Notional Value, Liabilities	$ 5,982	$ 2,559
Fair Value, Liabilities	$ 48	$ 7
Derivative Liability Average Remaining Maturity Period	1 month 6 days	1 month 13 days
Other Economic Hedges [Member] | Interest Rate Contracts [Member] | Options [Member] | Purchased [Member]
Derivative [Line Items]
Notional Value, Assets	$ 2,000	$ 2,935
Derivative Asset Average Remaining Maturity Period	22 days	22 days
Other Economic Hedges [Member] | Interest Rate Contracts [Member] | Options [Member] | Written [Member]
Derivative [Line Items]
Notional Value, Assets	$ 3,532	$ 3,199
Fair Value, Assets	$ 47	$ 29
Derivative Asset Average Remaining Maturity Period	1 month 13 days	1 month 6 days
Notional Value, Liabilities	$ 9	$ 5
Fair Value, Liabilities	$ 1	$ 1
Derivative Liability Average Remaining Maturity Period	1 month 6 days	29 days
Other Economic Hedges [Member] | Foreign Exchange Forward Contracts [Member]
Derivative [Line Items]
Notional Value, Assets	$ 4,735	$ 3,023
Fair Value, Assets	$ 56	$ 13
Derivative Asset Average Remaining Maturity Period	4 days	4 days
Notional Value, Liabilities	$ 1,139	$ 2,380
Fair Value, Liabilities	$ 13	$ 10
Derivative Liability Average Remaining Maturity Period	11 days	11 days
Other Economic Hedges [Member] | Equity Contracts [Member]
Derivative [Line Items]
Notional Value, Assets	$ 62	$ 62
Fair Value, Assets	$ 2
Derivative Asset Average Remaining Maturity Period	2 months 19 days	5 months 19 days
Notional Value, Liabilities	$ 23	$ 24
Fair Value, Liabilities	$ 1	$ 1
Derivative Liability Average Remaining Maturity Period	6 months 29 days	9 months 26 days
Other Economic Hedges [Member] | Credit Contracts [Member]
Derivative [Line Items]
Notional Value, Assets	$ 1,206	$ 1,192
Fair Value, Assets	$ 1	$ 2
Derivative Asset Average Remaining Maturity Period	2 years 10 months 2 days	2 years 6 months 29 days
Notional Value, Liabilities	$ 3,175	$ 2,821
Fair Value, Liabilities	$ 4	$ 3
Derivative Liability Average Remaining Maturity Period	3 years 1 month 28 days	2 years 11 months 27 days