Fair Value Measurements - Fair Value of Assets and Liabilities Measured on Recurring Basis (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012
ASSETS MEASURED ON A RECURRING BASIS
Total derivative assets	$ 475	$ 693	$ 771
Principal Investments Indirect [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	417
Recurring [Member]
ASSETS MEASURED ON A RECURRING BASIS
Securities purchased under resale agreements	516	271	294
Commercial loans	3	9	5
Total trading account assets	806	605	663
Securities available for sale	24	12,094	11,962
Total other investments	613	668	711
Derivative assets	1,344	1,963	2,147
Netting adjustments	(869)	(1,270)	(1,376)
Total derivative assets	475	693	771
Accrued income and other assets	48	3	138
Total assets at fair value	15,064	14,334	14,539
LIABILITIES MEASURED ON A RECURRING BASIS
Securities sold under repurchase agreements	464	228	398
Short positions	462	287	388
Derivative liabilities	1,009	1,387	1,562
Netting adjustments	(559)	(803)	(905)
Total derivative liabilities	450	584	657
Accrued expense and other liabilities	133	49	1
Total liabilities on a recurring basis at fair value	1,509	1,148	1,444
Recurring [Member] | U.S. Treasury, Agencies and Corporations [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	616	383	486
Recurring [Member] | States and Political Subdivisions [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	26	24	70
Securities available for sale		49	54
Recurring [Member] | Collateralized Mortgage Obligations [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	6	8	4
Securities available for sale	41	11,464	11,283
Recurring [Member] | Other Mortgage-Backed Securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	83	4	10
Securities available for sale	11,779	538	598
Recurring [Member] | Other Securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	72	177	88
Securities available for sale	762	43	27
Recurring [Member] | Total Trading Account Securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	803	596	658
Recurring [Member] | Principal Investments Direct [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	168	191	214
Recurring [Member] | Principal Investments Indirect [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	417	436	455
Recurring [Member] | Principal Investments [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	585	627	669
Recurring [Member] | Equity and Mezzanine Investments Indirect [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	28	41	42
Recurring [Member] | Private Equity and Mezzanine Investments [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	28	41	42
Recurring [Member] | Interest Rate [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	1,131	1,724	1,864
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	798	1,152	1,283
Recurring [Member] | Foreign Exchange [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	70	75	81
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	69	75	83
Recurring [Member] | Energy and Commodity [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	137	156	183
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	131	150	178
Recurring [Member] | Credit [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	6	8	19
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	11	10	18
Level 1 [Member] | Recurring [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account assets	6	2	10
Securities available for sale	24	43	27
Derivative assets	60	54	52
Total derivative assets	60	54	52
Total assets at fair value	90	99	89
LIABILITIES MEASURED ON A RECURRING BASIS
Short positions	4		4
Derivative liabilities	59	55	56
Total derivative liabilities	59	55	56
Accrued expense and other liabilities			1
Total liabilities on a recurring basis at fair value	63	55	61
Level 1 [Member] | Recurring [Member] | Other Securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	6	2	10
Securities available for sale		43	27
Level 1 [Member] | Recurring [Member] | Total Trading Account Securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	6	2	10
Level 1 [Member] | Recurring [Member] | Foreign Exchange [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	60	54	52
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	59	55	56
Level 2 [Member] | Recurring [Member]
ASSETS MEASURED ON A RECURRING BASIS
Securities purchased under resale agreements	516	271	294
Commercial loans	3	9	5
Total trading account assets	800	600	596
Securities available for sale		12,051	11,934
Derivative assets	1,261	1,883	2,067
Total derivative assets	1,261	1,883	2,067
Accrued income and other assets	48	3	138
Total assets at fair value	15,207	14,808	15,029
LIABILITIES MEASURED ON A RECURRING BASIS
Securities sold under repurchase agreements	464	228	398
Short positions	458	287	384
Derivative liabilities	948	1,330	1,504
Total derivative liabilities	948	1,330	1,504
Accrued expense and other liabilities	133	49
Total liabilities on a recurring basis at fair value	2,003	1,894	2,286
Level 2 [Member] | Recurring [Member] | U.S. Treasury, Agencies and Corporations [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	616	383	486
Level 2 [Member] | Recurring [Member] | States and Political Subdivisions [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	26	21	14
Securities available for sale		49	54
Level 2 [Member] | Recurring [Member] | Collateralized Mortgage Obligations [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	6	8	4
Securities available for sale	41	11,464	11,283
Level 2 [Member] | Recurring [Member] | Other Mortgage-Backed Securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	83	4	9
Securities available for sale	11,779	538	597
Level 2 [Member] | Recurring [Member] | Other Securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	66	175	78
Securities available for sale	762
Level 2 [Member] | Recurring [Member] | Total Trading Account Securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities	797	591	591
Level 2 [Member] | Recurring [Member] | Interest Rate [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	1,112	1,705	1,841
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	798	1,152	1,283
Level 2 [Member] | Recurring [Member] | Foreign Exchange [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	10	21	29
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	10	20	27
Level 2 [Member] | Recurring [Member] | Energy and Commodity [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	137	154	183
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	130	149	177
Level 2 [Member] | Recurring [Member] | Credit [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	2	3	14
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	10	9	17
Level 3 [Member] | Recurring [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account assets		3	57
Securities available for sale			1
Total other investments	613	668	711
Derivative assets	23	26	28
Total derivative assets	23	26	28
Total assets at fair value	636	697	797
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	2	2	2
Total derivative liabilities	2	2	2
Total liabilities on a recurring basis at fair value	2	2	2
Level 3 [Member] | Recurring [Member] | States and Political Subdivisions [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities		3	56
Level 3 [Member] | Recurring [Member] | Other Mortgage-Backed Securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities			1
Securities available for sale			1
Level 3 [Member] | Recurring [Member] | Total Trading Account Securities [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total trading account securities		3	57
Level 3 [Member] | Recurring [Member] | Principal Investments Direct [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	168	191	214
Level 3 [Member] | Recurring [Member] | Principal Investments Indirect [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	417	436	455
Level 3 [Member] | Recurring [Member] | Principal Investments [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	585	627	669
Level 3 [Member] | Recurring [Member] | Equity and Mezzanine Investments Indirect [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	28	41	42
Level 3 [Member] | Recurring [Member] | Private Equity and Mezzanine Investments [Member]
ASSETS MEASURED ON A RECURRING BASIS
Total other investments	28	41	42
Level 3 [Member] | Recurring [Member] | Interest Rate [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	19	19	23
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	1
Level 3 [Member] | Recurring [Member] | Credit [Member]
ASSETS MEASURED ON A RECURRING BASIS
Derivative assets	4	5	5
LIABILITIES MEASURED ON A RECURRING BASIS
Derivative liabilities	$ 1	$ 1	$ 1