ALLOWANCE FOR CREDIT LOSSES - Allowance for Loan Losses Roll Forward by Segment (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Dec. 31, 2016
Allowance for credit losses
Allowance for loan losses at beginning of period	$ 12,030	$ 12,712	$ 12,060	$ 12,626
Charge-offs	(2,130)	(2,048)	(4,274)	(4,191)
Recoveries	420	432	855	851
Replenishment of net charge-offs	1,710	1,616	3,419	3,340
Net reserve builds (releases)	67	(90)	47	(48)
Net specific reserve releases	(111)	(136)	(125)	(16)
Other	39	(182)	43	(258)
Allowance for loan losses at end of period	12,025	12,304	12,025	12,304
Allowance for loan losses
Collectively evaluated in accordance with ASC 450					$ 10,225	$ 10,054
Individually evaluated in accordance with ASC 310-10-35					1,795	2,000
Purchased credit-impaired in accordance with ASC 310-30					5	6
Total allowance for loan losses	12,030	12,712	12,060	12,626	12,025	12,060
Loans, net of unearned income
Collectively evaluated in accordance with ASC 450					631,121	610,342
Individually evaluated in accordance with ASC 310-10-35					9,175	10,354
Held at fair value					4,216	3,486
Loans, net of unearned income					644,695	624,369
Receivables Acquired with Deteriorated Credit Quality
Loans, net of unearned income
Purchased credit-impaired in accordance with ASC 310-30					183	187
Corporate
Allowance for credit losses
Allowance for loan losses at beginning of period	2,535	2,905	2,702	2,791
Charge-offs	(96)	(157)	(199)	(381)
Recoveries	19	16	85	30
Replenishment of net charge-offs	77	141	114	351
Net reserve builds (releases)	(4)	(16)	(170)	(12)
Net specific reserve releases	(27)	(11)	(39)	90
Other	6	(6)	17	3
Allowance for loan losses at end of period	2,510	2,872	2,510	2,872
Allowance for loan losses
Collectively evaluated in accordance with ASC 450					2,156	2,310
Individually evaluated in accordance with ASC 310-10-35					354	392
Purchased credit-impaired in accordance with ASC 310-30					0	0
Total allowance for loan losses	2,535	2,905	2,702	2,791	2,510	2,702
Loans, net of unearned income
Collectively evaluated in accordance with ASC 450					313,092	293,294
Individually evaluated in accordance with ASC 310-10-35					2,153	2,555
Held at fair value					4,189	3,457
Loans, net of unearned income					319,434	299,306
Corporate | Receivables Acquired with Deteriorated Credit Quality
Loans, net of unearned income
Purchased credit-impaired in accordance with ASC 310-30					0	0
Consumer
Allowance for credit losses
Allowance for loan losses at beginning of period	9,495	9,807	9,358	9,835
Charge-offs	(2,034)	(1,891)	(4,075)	(3,810)
Recoveries	401	416	770	821
Replenishment of net charge-offs	1,633	1,475	3,305	2,989
Net reserve builds (releases)	71	(74)	217	(36)
Net specific reserve releases	(84)	(125)	(86)	(106)
Other	33	(176)	26	(261)
Allowance for loan losses at end of period	9,515	9,432	9,515	9,432
Allowance for loan losses
Collectively evaluated in accordance with ASC 450					8,069	7,744
Individually evaluated in accordance with ASC 310-10-35					1,441	1,608
Purchased credit-impaired in accordance with ASC 310-30					5	6
Total allowance for loan losses	$ 9,495	$ 9,807	$ 9,358	$ 9,835	9,515	9,358
Loans, net of unearned income
Collectively evaluated in accordance with ASC 450					318,029	317,048
Individually evaluated in accordance with ASC 310-10-35					7,022	7,799
Held at fair value					27	29
Loans, net of unearned income					325,261	325,063
Consumer | Receivables Acquired with Deteriorated Credit Quality
Loans, net of unearned income
Purchased credit-impaired in accordance with ASC 310-30					$ 183	$ 187