Fair Value Measurements - Fair Value of Assets and Liabilities Measured on Recurring Basis (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012
ASSETS MEASURED ON A RECURRING BASIS
Total derivative assets	$ 461	$ 693	$ 818
Principal Investments Direct [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	426
Recurring [Member]
ASSETS MEASURED ON A RECURRING BASIS
Securities purchased under resale agreements	334	271	338
Commercial loans	10	9
Total trading account assets	592	605	679
Securities available for sale	13,253	12,094	13,205
Total other investments	644	668	785
Derivative assets	1,453	1,963	2,200
Netting adjustments	(992)	(1,270)	(1,382)
Total derivative assets	461	693	818
Accrued income and other assets	41	3	136
Total assets at fair value	15,325	14,334	15,961
LIABILITIES MEASURED ON A RECURRING BASIS
Securities sold under repurchase agreements	351	228	481
Short positions	298	287	363
Derivative liabilities	1,089	1,387	1,643
Netting adjustments	(633)	(803)	(880)
Total derivative liabilities	456	584	763
Accrued expense and other liabilities	2	49	4
Total liabilities on a recurring basis at fair value	1,107	1,148	1,611
Recurring [Member] | U.S. Treasury, Agencies and Corporations [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	375	383	438
Recurring [Member] | State and Political Subdivisions [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	28	24	84
Securities available for sale	44	49	56
Recurring [Member] | Collateralized Mortgage Obligations [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	38	8	16
Securities available for sale	12,603	11,464	12,477
Recurring [Member] | Other Mortgage-Backed Securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	67	4	101
Securities available for sale	584	538	652
Recurring [Member] | Other Securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	74	177	(40)
Securities available for sale	22	43	20
Recurring [Member] | Total Trading Account Securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	582	596	679
Recurring [Member] | Principal Investments Direct [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	186	191	242
Recurring [Member] | Principal Investments Indirect [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	426	436	482
Recurring [Member] | Principal Investments [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	612	627	724
Recurring [Member] | Equity and Mezzanine Investments Direct [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments			18
Recurring [Member] | Equity and Mezzanine Investments Indirect [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	32	41	43
Recurring [Member] | Private Equity and Mezzanine Investments [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	32	41	61
Recurring [Member] | Interest Rate [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	1,228	1,724	1,859
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	871	1,152	1,310
Recurring [Member] | Foreign Exchange [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	100	75	107
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	93	75	105
Recurring [Member] | Energy and Commodity [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	119	156	209
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	114	150	204
Recurring [Member] | Credit [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	6	8	25
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	11	10	24
Recurring [Member] | Equity [Member]
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities			24
Level 1 [Member] | Recurring [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account assets	3	2	3
Securities available for sale	22	43	20
Total other investments			11
Derivative assets	85	54	81
Total derivative assets	85	54	81
Accrued income and other assets	7		2
Total assets at fair value	117	99	117
LIABILITIES MEASURED ON A RECURRING BASIS
Short positions	4		3
Derivative liabilities	78	55	81
Total derivative liabilities	78	55	81
Total liabilities on a recurring basis at fair value	82	55	84
Level 1 [Member] | Recurring [Member] | Other Securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	3	2	(3)
Securities available for sale	22	43	20
Level 1 [Member] | Recurring [Member] | Total Trading Account Securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	3	2	3
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	85	54	81
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	78	55	81
Level 1 [Member] | Recurring [Member] | Energy and Commodity [Member]
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities			81
Level 2 [Member] | Recurring [Member]
ASSETS MEASURED ON A RECURRING BASIS
Securities purchased under resale agreements	334	271	338
Commercial loans	10	9
Total trading account assets	589	600	618
Securities available for sale	13,231	12,051	13,185
Derivative assets	1,337	1,883	2,078
Total derivative assets	1,337	1,883	2,078
Accrued income and other assets	34	3	134
Total assets at fair value	15,525	14,808	16,353
LIABILITIES MEASURED ON A RECURRING BASIS
Securities sold under repurchase agreements	351	228	481
Short positions	294	287	360
Derivative liabilities	1,010	1,330	1,560
Total derivative liabilities	1,010	1,330	1,560
Accrued expense and other liabilities	2	49	4
Total liabilities on a recurring basis at fair value	1,657	1,894	2,405
Level 2 [Member] | Recurring [Member] | U.S. Treasury, Agencies and Corporations [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	375	383	438
Level 2 [Member] | Recurring [Member] | State and Political Subdivisions [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	28	21	27
Securities available for sale	44	49	56
Level 2 [Member] | Recurring [Member] | Collateralized Mortgage Obligations [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	38	8	16
Securities available for sale	12,603	11,464	12,477
Level 2 [Member] | Recurring [Member] | Other Mortgage-Backed Securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	67	4	100
Securities available for sale	584	538	652
Level 2 [Member] | Recurring [Member] | Other Securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	71	175	(37)
Level 2 [Member] | Recurring [Member] | Total Trading Account Securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	579	591	618
Level 2 [Member] | Recurring [Member] | Interest Rate [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	1,203	1,705	1,824
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	871	1,152	1,310
Level 2 [Member] | Recurring [Member] | Foreign Exchange [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	15	21	26
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	15	20	24
Level 2 [Member] | Recurring [Member] | Energy and Commodity [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	117	154	209
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	113	149	203
Level 2 [Member] | Recurring [Member] | Credit [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	2	3	19
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	11	9	23
Level 2 [Member] | Recurring [Member] | Equity [Member]
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities			23
Level 3 [Member] | Recurring [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account assets		3	58
Total other investments	644	668	774
Derivative assets	31	26	41
Total derivative assets	31	26	41
Total assets at fair value	675	697	873
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	1	2	2
Total derivative liabilities	1	2	2
Total liabilities on a recurring basis at fair value	1	2	2
Level 3 [Member] | Recurring [Member] | State and Political Subdivisions [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities		3	57
Level 3 [Member] | Recurring [Member] | Other Mortgage-Backed Securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities			1
Level 3 [Member] | Recurring [Member] | Total Trading Account Securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities		3	58
Level 3 [Member] | Recurring [Member] | Principal Investments Direct [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	186	191	231
Level 3 [Member] | Recurring [Member] | Principal Investments Indirect [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	426	436	482
Level 3 [Member] | Recurring [Member] | Principal Investments [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	612	627	713
Level 3 [Member] | Recurring [Member] | Equity and Mezzanine Investments Direct [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments			18
Level 3 [Member] | Recurring [Member] | Equity and Mezzanine Investments Indirect [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	32	41	43
Level 3 [Member] | Recurring [Member] | Private Equity and Mezzanine Investments [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	32	41	61
Level 3 [Member] | Recurring [Member] | Interest Rate [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	25	19	35
Level 3 [Member] | Recurring [Member] | Energy and Commodity [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	2	2
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	1	1	1
Level 3 [Member] | Recurring [Member] | Credit [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	4	5	6
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities		1	1
Level 3 [Member] | Recurring [Member] | Equity [Member]
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities			$ 1