Derivative Instruments - Asset and Liability Management Derivative Positions of Company (Detail) - Asset and Liability Management Positions [Member] - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2016	Dec. 31, 2015
Derivative [Line Items]
Notional Value, Assets	$ 29,669	$ 27,442
Fair Value, Assets	806	201
Notional Value, Liabilities	24,593	22,818
Fair Value, Liabilities	827	286
Other Derivatives [Member]
Derivative [Line Items]
Notional Value, Assets	104	$ 36
Fair Value, Assets	$ 2
Derivative Asset Average Remaining Maturity Period	7 days	15 days
Notional Value, Liabilities	$ 785	$ 662
Fair Value, Liabilities	$ 100	$ 64
Derivative Liability Average Remaining Maturity Period	3 years 5 months 23 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	$ 3,800	$ 3,050
Fair Value, Assets	$ 163	$ 73
Derivative Asset Average Remaining Maturity Period	4 years 1 month 21 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		$ 1,772
Fair Value, Assets		$ 7
Derivative Asset Average Remaining Maturity Period		9 years 2 months 19 days
Notional Value, Liabilities	$ 7,524	$ 5,009
Fair Value, Liabilities	$ 241	$ 146
Derivative Liability Average Remaining Maturity Period	4 years 6 months 15 days	1 year 1 month 17 days
Net Investment Hedges [Member] | Foreign Exchange Forward Contracts [Member]
Derivative [Line Items]
Notional Value, Assets	$ 1,228	$ 1,140
Fair Value, Assets	$ 20	$ 4
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	$ 9,627	$ 3,733
Fair Value, Assets	$ 454	$ 42
Derivative Asset Average Remaining Maturity Period	9 years 10 months 17 days	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	$ 356	$ 35
Derivative Liability Average Remaining Maturity Period	9 years 5 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	$ 7,293	$ 3,812
Fair Value, Assets	$ 94	$ 17
Derivative Asset Average Remaining Maturity Period	29 days	26 days
Notional Value, Liabilities	$ 7	$ 452
Fair Value, Liabilities	$ 1	$ 1
Derivative Liability Average Remaining Maturity Period	1 month 6 days	22 days
Other Economic Hedges [Member] | Interest Rate Contracts [Member] | Futures and Forwards [Member] | Written [Member]
Derivative [Line Items]
Notional Value, Assets	$ 56	$ 3,201
Fair Value, Assets	$ 3	$ 12
Derivative Asset Average Remaining Maturity Period	2 months 19 days	1 month 2 days
Notional Value, Liabilities	$ 8,085	$ 2,559
Fair Value, Liabilities	$ 95	$ 7
Derivative Liability Average Remaining Maturity Period	1 month 10 days	1 month 13 days
Other Economic Hedges [Member] | Interest Rate Contracts [Member] | Options [Member] | Purchased [Member]
Derivative [Line Items]
Notional Value, Assets	$ 2,160	$ 2,935
Derivative Asset Average Remaining Maturity Period	29 days	22 days
Other Economic Hedges [Member] | Interest Rate Contracts [Member] | Options [Member] | Written [Member]
Derivative [Line Items]
Notional Value, Assets	$ 3,326	$ 3,199
Fair Value, Assets	$ 63	$ 29
Derivative Asset Average Remaining Maturity Period	1 month 6 days	1 month 6 days
Notional Value, Liabilities	$ 6	$ 5
Fair Value, Liabilities	$ 1	$ 1
Derivative Liability Average Remaining Maturity Period	29 days	29 days
Other Economic Hedges [Member] | Foreign Exchange Forward Contracts [Member]
Derivative [Line Items]
Notional Value, Assets	$ 575	$ 3,023
Fair Value, Assets	$ 5	$ 13
Derivative Asset Average Remaining Maturity Period	15 days	4 days
Notional Value, Liabilities	$ 586	$ 2,380
Fair Value, Liabilities	$ 28	$ 10
Derivative Liability Average Remaining Maturity Period	15 days	11 days
Other Economic Hedges [Member] | Equity Contracts [Member]
Derivative [Line Items]
Notional Value, Assets	$ 65	$ 62
Fair Value, Assets	$ 1
Derivative Asset Average Remaining Maturity Period	11 months 19 days	5 months 19 days
Notional Value, Liabilities	$ 34	$ 24
Fair Value, Liabilities	$ 1	$ 1
Derivative Liability Average Remaining Maturity Period	6 months 4 days	9 months 26 days
Other Economic Hedges [Member] | Credit Contracts [Member]
Derivative [Line Items]
Notional Value, Assets	$ 1,435	$ 1,192
Fair Value, Assets	$ 1	$ 2
Derivative Asset Average Remaining Maturity Period	3 years 2 months 27 days	2 years 6 months 29 days
Notional Value, Liabilities	$ 3,185	$ 2,821
Fair Value, Liabilities	$ 4	$ 3
Derivative Liability Average Remaining Maturity Period	3 years 3 months	2 years 11 months 27 days