Fair Value Measurements - Fair Value of Assets and Liabilities Measured on Recurring Basis (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
ASSETS MEASURED ON A RECURRING BASIS
Total derivative assets	$ 693	$ 945
Principal Investments Direct [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	436
Recurring [Member]
ASSETS MEASURED ON A RECURRING BASIS
Securities purchased under resale agreements	271	236
Commercial loans	9
Total trading account assets	605	623
Securities available for sale	12,094	16,012
Total other investments	668	760
Derivative assets	1,963	2,397
Netting adjustments	(1,270)	(1,452)
Total derivative assets	693	945
Accrued income and other assets	3	112
Total assets at fair value	14,334	18,688
LIABILITIES MEASURED ON A RECURRING BASIS
Securities sold under repurchase agreements	228	292
Short positions	287	337
Derivative liabilities	1,387	2,004
Netting adjustments	(803)	(978)
Total derivative liabilities	584	1,026
Accrued expense and other liabilities	49	45
Total liabilities on a recurring basis at fair value	1,148	1,700
Recurring [Member] | U.S. Treasury, agencies and corporations [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	383	353
Recurring [Member] | States and political subdivisions [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	24	81
Securities available for sale	49	63
Recurring [Member] | Collateralized mortgage obligations [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	8	19
Securities available for sale	11,464	15,162
Recurring [Member] | Other Mortgage-Backed Securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	4	62
Securities available for sale	538	778
Recurring [Member] | Other securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	177	108
Securities available for sale	43	9
Recurring [Member] | Total trading account securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	596	623
Recurring [Member] | Principal Investments Direct [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	191	236
Recurring [Member] | Principal Investments Indirect [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	436	473
Recurring [Member] | Principal investments [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	627	709
Recurring [Member] | Equity And Mezzanine Investments Direct [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments		15
Recurring [Member] | Equity And Mezzanine Investments Indirect [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	41	36
Recurring [Member] | Private equity and mezzanine investments [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	41	51
Recurring [Member] | Interest Rate [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	1,724	1,953
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	1,152	1,398
Recurring [Member] | Foreign exchange [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	75	151
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	75	288
Recurring [Member] | Energy and Commodity [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	156	253
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	150	253
Recurring [Member] | Credit [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	8	37
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	10	62
Recurring [Member] | Equity [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets		3
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities		3
Level 1 [Member] | Recurring [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account assets	2	79
Securities available for sale	43	9
Total other investments		11
Derivative assets	54	86
Total derivative assets	54	86
Accrued income and other assets		7
Total assets at fair value	99	192
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	55	79
Total derivative liabilities	55	79
Accrued expense and other liabilities		23
Total liabilities on a recurring basis at fair value	55	102
Level 1 [Member] | Recurring [Member] | Other securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	2	79
Securities available for sale	43	9
Level 1 [Member] | Recurring [Member] | Total trading account securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	2	79
Level 1 [Member] | Recurring [Member] | Principal Investments Direct [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments		11
Level 1 [Member] | Recurring [Member] | Principal investments [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments		11
Level 1 [Member] | Recurring [Member] | Foreign exchange [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	54	86
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	55	79
Level 2 [Member] | Recurring [Member]
ASSETS MEASURED ON A RECURRING BASIS
Securities purchased under resale agreements	271	236
Commercial loans	9
Total trading account assets	600	509
Securities available for sale	12,051	16,003
Derivative assets	1,883	2,266
Total derivative assets	1,883	2,266
Accrued income and other assets	3	105
Total assets at fair value	14,808	19,119
LIABILITIES MEASURED ON A RECURRING BASIS
Securities sold under repurchase agreements	228	292
Short positions	287	337
Derivative liabilities	1,330	1,896
Total derivative liabilities	1,330	1,896
Accrued expense and other liabilities	49	22
Total liabilities on a recurring basis at fair value	1,894	2,547
Level 2 [Member] | Recurring [Member] | U.S. Treasury, agencies and corporations [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	383	353
Level 2 [Member] | Recurring [Member] | States and political subdivisions [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	21	81
Securities available for sale	49	63
Level 2 [Member] | Recurring [Member] | Collateralized mortgage obligations [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	8	19
Securities available for sale	11,464	15,162
Level 2 [Member] | Recurring [Member] | Other Mortgage-Backed Securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	4	27
Securities available for sale	538	778
Level 2 [Member] | Recurring [Member] | Other securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	175	29
Level 2 [Member] | Recurring [Member] | Total trading account securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	591	509
Level 2 [Member] | Recurring [Member] | Interest Rate [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	1,705	1,915
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	1,152	1,398
Level 2 [Member] | Recurring [Member] | Foreign exchange [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	21	65
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	20	209
Level 2 [Member] | Recurring [Member] | Energy and Commodity [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	154	253
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	149	252
Level 2 [Member] | Recurring [Member] | Credit [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	3	30
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	9	34
Level 2 [Member] | Recurring [Member] | Equity [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets		3
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities		3
Level 3 [Member] | Recurring [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account assets	3	35
Total other investments	668	749
Derivative assets	26	45
Total derivative assets	26	45
Total assets at fair value	697	829
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	2	29
Total derivative liabilities	2	29
Total liabilities on a recurring basis at fair value	2	29
Level 3 [Member] | Recurring [Member] | States and political subdivisions [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	3
Level 3 [Member] | Recurring [Member] | Other Mortgage-Backed Securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities		35
Level 3 [Member] | Recurring [Member] | Total trading account securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	3	35
Level 3 [Member] | Recurring [Member] | Principal Investments Direct [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	191	225
Level 3 [Member] | Recurring [Member] | Principal Investments Indirect [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	436	473
Level 3 [Member] | Recurring [Member] | Principal investments [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	627	698
Level 3 [Member] | Recurring [Member] | Equity And Mezzanine Investments Direct [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments		15
Level 3 [Member] | Recurring [Member] | Equity And Mezzanine Investments Indirect [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	41	36
Level 3 [Member] | Recurring [Member] | Private equity and mezzanine investments [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	41	51
Level 3 [Member] | Recurring [Member] | Interest Rate [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	19	38
Level 3 [Member] | Recurring [Member] | Energy and Commodity [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	2
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	1	1
Level 3 [Member] | Recurring [Member] | Credit [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	5	7
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	$ 1	$ 28