FAIR VALUE MEASUREMENT (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Interest-bearing deposits | Recurring
Fair value, liabilities measured on recurring basis, level 3 fair-value category reconciliation
Balance at beginning of period, liability	$ 786	$ 431
Net realized/unrealized gains (losses) included in locations other than principal transactions, liabilities	(16)	(5)
Transfers into Level 3, liabilities	22	83
Issuance, liability	25	8
Settlements, liability	(15)	(69)
Balance at end of period, liability	834	458
Unrealized gains (losses) still held, liabilities	(56)	(58)
Federal funds purchased and securities loaned or sold under agreements to repurchase | Recurring
Fair value, liabilities measured on recurring basis, level 3 fair-value category reconciliation
Balance at beginning of period, liability	841	1,061
Net realized/unrealized gains (losses) included in principal transactions, liabilities	27	27
Transfers into Level 3, liabilities	201
Sales, liability	38
Settlements, liability		(9)
Balance at end of period, liability	1,053	1,025
Unrealized gains (losses) still held, liabilities	14
Trading account liabilities | Securities sold, not yet purchased | Recurring
Fair value, liabilities measured on recurring basis, level 3 fair-value category reconciliation
Balance at beginning of period, liability	365	412
Net realized/unrealized gains (losses) included in principal transactions, liabilities	19	(72)
Transfers into Level 3, liabilities	20	4
Transfers out of Level 3, liabilities	(5)	(7)
Sales, liability	46	71
Settlements, liability	(72)	(375)
Balance at end of period, liability	335	177
Unrealized gains (losses) still held, liabilities	125	(75)
Short-term borrowings | Recurring
Fair value, liabilities measured on recurring basis, level 3 fair-value category reconciliation
Balance at beginning of period, liability	112	499
Net realized/unrealized gains (losses) included in principal transactions, liabilities	42	(56)
Transfers out of Level 3, liabilities		(9)
Issuance, liability	1	126
Settlements, liability	(18)	(249)
Balance at end of period, liability	53	423
Unrealized gains (losses) still held, liabilities	(19)	(2)
Long-term debt | Recurring
Fair value, liabilities measured on recurring basis, level 3 fair-value category reconciliation
Balance at beginning of period, liability	6,726	6,904
Net realized/unrealized gains (losses) included in principal transactions, liabilities	(9)	(78)
Net realized/unrealized gains (losses) included in locations other than principal transactions, liabilities	33	29
Transfers into Level 3, liabilities	635	159
Transfers out of Level 3, liabilities	(465)	(416)
Issuance, liability	284	287
Sales, liability	(1)
Settlements, liability	(308)	(464)
Balance at end of period, liability	6,847	6,519
Unrealized gains (losses) still held, liabilities	(113)	(203)
Other financial liabilities measured on a recurring basis | Recurring
Fair value, liabilities measured on recurring basis, level 3 fair-value category reconciliation
Balance at beginning of period, liability	24	3
Net realized/unrealized gains (losses) included in locations other than principal transactions, liabilities	1	(1)
Transfers into Level 3, liabilities	2
Transfers out of Level 3, liabilities	(2)
Purchases, liability	(2)	(1)
Issuance, liability	2
Settlements, liability	(7)	(1)
Balance at end of period, liability	16	2
Unrealized gains (losses) still held, liabilities		(1)
Federal funds sold and securities borrowed or purchased under agreements to resell
Fair value, assets measured on recurring basis, level 3 fair-value category reconciliation
Threshold Tenor of Repo Curves to Classify Structured Reverse Repos as Level 3	5 years
Federal funds sold and securities borrowed or purchased under agreements to resell | Recurring
Fair value, assets measured on recurring basis, level 3 fair-value category reconciliation
Balance at beginning of period, asset	5,043	4,701
Net realized/unrealized gains (losses) included in principal transactions, assets	(13)	33
Transfers into Level 3, assets	598	25
Transfers out of Level 3, assets	(1,279)	(262)
Balance at end of period, asset	4,349	4,497
Unrealized gains (losses) still held, assets	(43)	32
Trading account assets | Recurring
Fair value, assets measured on recurring basis, level 3 fair-value category reconciliation
Balance at beginning of period, asset	13,823	15,792
Net realized/unrealized gains (losses) included in principal transactions, assets	532	429
Transfers into Level 3, assets	861	1,020
Transfers out of Level 3, assets	(1,189)	(1,097)
Purchases, assets	4,131	6,998
Issuance, assets	26	31
Sales, assets	(4,741)	(5,622)
Settlements, assets	(521)	(863)
Balance at end of period, asset	12,922	16,688
Unrealized gains (losses) still held, assets	(250)	198
Trading account assets | Mortgage-backed securities | Recurring
Fair value, assets measured on recurring basis, level 3 fair-value category reconciliation
Balance at beginning of period, asset	4,249	2,988
Net realized/unrealized gains (losses) included in principal transactions, assets	274	2
Transfers into Level 3, assets	579	445
Transfers out of Level 3, assets	(614)	(415)
Purchases, assets	1,074	1,086
Issuance, assets	26	31
Sales, assets	(1,740)	(1,088)
Settlements, assets	(48)	(39)
Balance at end of period, asset	3,800	3,010
Unrealized gains (losses) still held, assets	87	36
Trading account assets | U.S. government-sponsored agency guaranteed | Recurring
Fair value, assets measured on recurring basis, level 3 fair-value category reconciliation
Balance at beginning of period, asset	1,325	861
Net realized/unrealized gains (losses) included in principal transactions, assets	49	50
Transfers into Level 3, assets	392	379
Transfers out of Level 3, assets	(402)	(127)
Purchases, assets	280	183
Issuance, assets	26	31
Sales, assets	(368)	(225)
Settlements, assets	(24)	(37)
Balance at end of period, asset	1,278	1,115
Unrealized gains (losses) still held, assets	30	22
Trading account assets | Residential | Recurring
Fair value, assets measured on recurring basis, level 3 fair-value category reconciliation
Balance at beginning of period, asset	1,805	1,509
Net realized/unrealized gains (losses) included in principal transactions, assets	171	19
Transfers into Level 3, assets	98	30
Transfers out of Level 3, assets	(176)	(180)
Purchases, assets	727	692
Sales, assets	(506)	(721)
Settlements, assets	(7)	(2)
Balance at end of period, asset	2,112	1,347
Unrealized gains (losses) still held, assets	56	12
Trading account assets | Commercial | Recurring
Fair value, assets measured on recurring basis, level 3 fair-value category reconciliation
Balance at beginning of period, asset	1,119	618
Net realized/unrealized gains (losses) included in principal transactions, assets	54	(67)
Transfers into Level 3, assets	89	36
Transfers out of Level 3, assets	(36)	(108)
Purchases, assets	67	211
Sales, assets	(866)	(142)
Settlements, assets	(17)
Balance at end of period, asset	410	548
Unrealized gains (losses) still held, assets	1	2
Trading account assets | U.S. Treasury and federal agency securities | Recurring
Fair value, assets measured on recurring basis, level 3 fair-value category reconciliation
Balance at beginning of period, asset		3
Sales, assets		(3)
Trading account assets | State and municipal securities | Recurring
Fair value, assets measured on recurring basis, level 3 fair-value category reconciliation
Balance at beginning of period, asset	195	252
Net realized/unrealized gains (losses) included in principal transactions, assets	1	(3)
Purchases, assets	19	22
Sales, assets	(6)	(48)
Balance at end of period, asset	209	223
Unrealized gains (losses) still held, assets	2	(4)
Trading account assets | Foreign government | Recurring
Fair value, assets measured on recurring basis, level 3 fair-value category reconciliation
Balance at beginning of period, asset	311	521
Net realized/unrealized gains (losses) included in principal transactions, assets	2	3
Transfers into Level 3, assets	6	2
Transfers out of Level 3, assets	(36)	(263)
Purchases, assets	65	710
Sales, assets	(120)	(140)
Balance at end of period, asset	228	833
Unrealized gains (losses) still held, assets	1	4
Trading account assets | Corporate | Recurring
Fair value, assets measured on recurring basis, level 3 fair-value category reconciliation
Balance at beginning of period, asset	2,030	3,240
Net realized/unrealized gains (losses) included in principal transactions, assets	(104)	119
Transfers into Level 3, assets	76	327
Transfers out of Level 3, assets	(17)	(125)
Purchases, assets	568	1,496
Sales, assets	(443)	(595)
Settlements, assets	(374)	(699)
Balance at end of period, asset	1,736	3,763
Unrealized gains (losses) still held, assets	(303)	121
Trading account assets | Equity securities | Recurring
Fair value, assets measured on recurring basis, level 3 fair-value category reconciliation
Balance at beginning of period, asset	264	244
Net realized/unrealized gains (losses) included in principal transactions, assets	37	4
Transfers into Level 3, assets	23	18
Transfers out of Level 3, assets	(63)	(9)
Purchases, assets	78	78
Sales, assets	(60)	(120)
Settlements, assets		(24)
Balance at end of period, asset	279	191
Unrealized gains (losses) still held, assets	23	(3)
Trading account assets | Asset-backed securities | Recurring
Fair value, assets measured on recurring basis, level 3 fair-value category reconciliation
Balance at beginning of period, asset	4,453	5,801
Net realized/unrealized gains (losses) included in principal transactions, assets	224	335
Transfers into Level 3, assets	38	17
Transfers out of Level 3, assets	(32)	(36)
Purchases, assets	1,583	2,651
Sales, assets	(1,856)	(3,054)
Settlements, assets		(59)
Balance at end of period, asset	4,410	5,655
Unrealized gains (losses) still held, assets	(53)	66
Trading account assets | Other debt securities | Recurring
Fair value, assets measured on recurring basis, level 3 fair-value category reconciliation
Balance at beginning of period, asset	2,321	2,743
Net realized/unrealized gains (losses) included in principal transactions, assets	98	(31)
Transfers into Level 3, assets	139	211
Transfers out of Level 3, assets	(427)	(249)
Purchases, assets	744	955
Sales, assets	(516)	(574)
Settlements, assets	(99)	(42)
Balance at end of period, asset	2,260	3,013
Unrealized gains (losses) still held, assets	(7)	(22)
Derivatives | Recurring
Fair value, assets measured on recurring basis, level 3 fair-value category reconciliation
Balance at beginning of period, asset	(2,380)	(779)
Net realized/unrealized gains (losses) included in principal transactions, assets	114	(731)
Transfers into Level 3, assets	833	131
Transfers out of Level 3, assets	(227)	367
Purchases, assets	160	618
Sales, assets	(90)	(489)
Settlements, assets	76	(504)
Balance at end of period, asset	(1,514)	(1,387)
Unrealized gains (losses) still held, assets	(29)	(1,590)
Investments: | Recurring
Fair value, assets measured on recurring basis, level 3 fair-value category reconciliation
Balance at beginning of period, asset	11,907	16,797
Net realized/unrealized gains (losses) included in locations other than principal transactions, assets	106	251
Transfers into Level 3, assets	3,014
Transfers out of Level 3, assets	(1,744)	(782)
Purchases, assets	1,546	1,237
Sales, assets	(314)	(354)
Settlements, assets	(510)	(1,349)
Balance at end of period, asset	14,005	15,800
Unrealized gains (losses) still held, assets	35	246
Investments: | Mortgage-backed securities | Recurring
Fair value, assets measured on recurring basis, level 3 fair-value category reconciliation
Balance at beginning of period, asset	1,663	687
Net realized/unrealized gains (losses) included in locations other than principal transactions, assets	12	9
Transfers into Level 3, assets	1,693
Transfers out of Level 3, assets	(1,236)	(647)
Purchases, assets	588	891
Settlements, assets	(8)
Balance at end of period, asset	2,712	940
Unrealized gains (losses) still held, assets	12	4
Investments: | U.S. government-sponsored agency guaranteed | Recurring
Fair value, assets measured on recurring basis, level 3 fair-value category reconciliation
Balance at beginning of period, asset	1,458	679
Net realized/unrealized gains (losses) included in locations other than principal transactions, assets	3	9
Transfers into Level 3, assets	1,633
Transfers out of Level 3, assets	(1,031)	(641)
Purchases, assets	471	885
Settlements, assets	(8)
Balance at end of period, asset	2,526	932
Unrealized gains (losses) still held, assets	3	4
Investments: | Residential | Recurring
Fair value, assets measured on recurring basis, level 3 fair-value category reconciliation
Balance at beginning of period, asset	205	8
Net realized/unrealized gains (losses) included in locations other than principal transactions, assets	9
Transfers into Level 3, assets	60
Transfers out of Level 3, assets	(205)	(6)
Purchases, assets	117
Balance at end of period, asset	186	2
Unrealized gains (losses) still held, assets	9
Investments: | Commercial | Recurring
Fair value, assets measured on recurring basis, level 3 fair-value category reconciliation
Purchases, assets		6
Balance at end of period, asset		6
Investments: | U.S. Treasury and federal agency securities | Recurring
Fair value, assets measured on recurring basis, level 3 fair-value category reconciliation
Balance at beginning of period, asset	12	75
Transfers out of Level 3, assets		(75)
Sales, assets	(1)
Balance at end of period, asset	11
Investments: | State and municipal securities | Recurring
Fair value, assets measured on recurring basis, level 3 fair-value category reconciliation
Balance at beginning of period, asset	849	667
Net realized/unrealized gains (losses) included in locations other than principal transactions, assets	(17)	(1)
Transfers into Level 3, assets	7
Transfers out of Level 3, assets	(117)
Purchases, assets	81	32
Sales, assets	(55)	(16)
Balance at end of period, asset	748	682
Unrealized gains (losses) still held, assets	(40)	(7)
Investments: | Foreign government | Recurring
Fair value, assets measured on recurring basis, level 3 fair-value category reconciliation
Balance at beginning of period, asset	383	447
Net realized/unrealized gains (losses) included in locations other than principal transactions, assets	1	3
Transfers into Level 3, assets	22
Transfers out of Level 3, assets	(174)	(17)
Purchases, assets	130	89
Sales, assets	(67)	(80)
Settlements, assets	(27)	(67)
Balance at end of period, asset	268	375
Unrealized gains (losses) still held, assets	(4)	1
Investments: | Corporate | Recurring
Fair value, assets measured on recurring basis, level 3 fair-value category reconciliation
Balance at beginning of period, asset	385	989
Net realized/unrealized gains (losses) included in locations other than principal transactions, assets	1	(4)
Transfers into Level 3, assets	100
Transfers out of Level 3, assets	(12)
Purchases, assets	14	87
Sales, assets	(143)	(7)
Settlements, assets		(3)
Balance at end of period, asset	345	1,062
Unrealized gains (losses) still held, assets		1
Investments: | Equity securities | Recurring
Fair value, assets measured on recurring basis, level 3 fair-value category reconciliation
Balance at beginning of period, asset	773	1,453
Net realized/unrealized gains (losses) included in locations other than principal transactions, assets	2	45
Purchases, assets	1
Sales, assets	(9)	(172)
Balance at end of period, asset	767	1,326
Unrealized gains (losses) still held, assets	1	16
Investments: | Asset-backed securities | Recurring
Fair value, assets measured on recurring basis, level 3 fair-value category reconciliation
Balance at beginning of period, asset	2,220	4,041
Net realized/unrealized gains (losses) included in locations other than principal transactions, assets	38	3
Transfers into Level 3, assets	1,192
Transfers out of Level 3, assets		(43)
Purchases, assets	692
Sales, assets	(17)	(7)
Settlements, assets	(310)	(921)
Balance at end of period, asset	3,815	3,073
Unrealized gains (losses) still held, assets	(70)
Investments: | Other debt securities | Recurring
Fair value, assets measured on recurring basis, level 3 fair-value category reconciliation
Balance at beginning of period, asset	258	120
Transfers out of Level 3, assets	(205)
Sales, assets	(1)	(64)
Settlements, assets		(1)
Balance at end of period, asset	52	55
Investments: | Non-marketable equity securities | Recurring
Fair value, assets measured on recurring basis, level 3 fair-value category reconciliation
Balance at beginning of period, asset	5,364	8,318
Net realized/unrealized gains (losses) included in locations other than principal transactions, assets	69	196
Purchases, assets	40	138
Sales, assets	(21)	(8)
Settlements, assets	(165)	(357)
Balance at end of period, asset	5,287	8,287
Unrealized gains (losses) still held, assets	136	231
Loans | Recurring
Fair value, assets measured on recurring basis, level 3 fair-value category reconciliation
Balance at beginning of period, asset	4,931	4,682
Net realized/unrealized gains (losses) included in locations other than principal transactions, assets	(75)	(37)
Transfers out of Level 3, assets		(25)
Purchases, assets	95	86
Issuance, assets	7
Sales, assets	(63)	(8)
Settlements, assets	(381)	(420)
Balance at end of period, asset	4,514	4,278
Unrealized gains (losses) still held, assets	(26)	300
Mortgage servicing rights | Recurring
Fair value, assets measured on recurring basis, level 3 fair-value category reconciliation
Balance at beginning of period, asset	1,942	2,569
Net realized/unrealized gains (losses) included in locations other than principal transactions, assets	190	187
Purchases, assets		2
Issuance, assets	172	142
Sales, assets	(1)	(5)
Settlements, assets	(100)	(204)
Balance at end of period, asset	2,203	2,691
Unrealized gains (losses) still held, assets	191	184
Other financial assets measured on a recurring basis | Recurring
Fair value, assets measured on recurring basis, level 3 fair-value category reconciliation
Balance at beginning of period, asset	2,452	2,245
Net realized/unrealized gains (losses) included in locations other than principal transactions, assets	36	7
Transfers into Level 3, assets	1	8
Transfers out of Level 3, assets		(1)
Purchases, assets	138	1
Issuance, assets	290	276
Sales, assets	(5)	(38)
Settlements, assets	(484)	(176)
Balance at end of period, asset	2,428	2,322
Unrealized gains (losses) still held, assets	32	14
Interest rate contracts | Derivatives | Recurring
Fair value, assets measured on recurring basis, level 3 fair-value category reconciliation
Balance at beginning of period, asset	181	726
Net realized/unrealized gains (losses) included in principal transactions, assets	(27)	(217)
Transfers into Level 3, assets	829	342
Transfers out of Level 3, assets	(167)	(17)
Purchases, assets	91	199
Sales, assets	(15)	(129)
Settlements, assets	(279)	(213)
Balance at end of period, asset	613	691
Unrealized gains (losses) still held, assets	(43)	(456)
Foreign exchange contracts | Derivatives | Recurring
Fair value, assets measured on recurring basis, level 3 fair-value category reconciliation
Balance at beginning of period, asset		(562)
Net realized/unrealized gains (losses) included in principal transactions, assets	98	173
Transfers into Level 3, assets	10	(5)
Transfers out of Level 3, assets	(10)	(8)
Purchases, assets	9	129
Sales, assets	(7)	(107)
Settlements, assets	40	10
Balance at end of period, asset	140	(370)
Unrealized gains (losses) still held, assets	(128)	29
Equity contracts | Derivatives | Recurring
Fair value, assets measured on recurring basis, level 3 fair-value category reconciliation
Balance at beginning of period, asset	(1,448)	(1,737)
Net realized/unrealized gains (losses) included in principal transactions, assets	92	474
Transfers into Level 3, assets	(22)	3
Transfers out of Level 3, assets	81	436
Purchases, assets	49	134
Sales, assets	(61)	(175)
Settlements, assets	(165)	(212)
Balance at end of period, asset	(1,474)	(1,077)
Unrealized gains (losses) still held, assets	(101)	(135)
Commodity and other contracts | Derivatives | Recurring
Fair value, assets measured on recurring basis, level 3 fair-value category reconciliation
Balance at beginning of period, asset	(771)	(934)
Net realized/unrealized gains (losses) included in principal transactions, assets	54	74
Transfers into Level 3, assets	8	(5)
Transfers out of Level 3, assets	(2)	9
Purchases, assets	3	45
Sales, assets	(7)	(68)
Settlements, assets	78	20
Balance at end of period, asset	(637)	(859)
Unrealized gains (losses) still held, assets	137	2
Credit derivatives | Derivatives | Recurring
Fair value, assets measured on recurring basis, level 3 fair-value category reconciliation
Balance at beginning of period, asset	(342)	1,728
Net realized/unrealized gains (losses) included in principal transactions, assets	(103)	(1,235)
Transfers into Level 3, assets	8	(204)
Transfers out of Level 3, assets	(129)	(53)
Purchases, assets	8	111
Sales, assets		(10)
Settlements, assets	402	(109)
Balance at end of period, asset	(156)	228
Unrealized gains (losses) still held, assets	$ 106	$ (1,030)