LOANS - Consumer Loan Delinquency (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Non-Accrual Details
Loans, net of unearned income	$ 644,695	$ 624,369
Loans at fair value	4,216	3,486
Consumer
Non-Accrual Details
Loans, current	318,124	317,187
Loans, net of unearned income	325,261	325,063
Total non-accrual	2,848	3,158
90 days past due and accruing	$ 2,652	$ 2,991
Loans less than this number of days past due are considered current	30 days	30 days
Number of days past due, non-accrual status	60 days
Consumer | Less than or equal to 80%
Financing Receivable
Purchased credit-impaired in accordance with ASC 310-30	$ 56,917	$ 58,718
Consumer | 80% but less than or equal to 100%
Financing Receivable
Purchased credit-impaired in accordance with ASC 310-30	5,676	7,120
Consumer | Greater than 100%
Financing Receivable
Purchased credit-impaired in accordance with ASC 310-30	1,199	1,629
Consumer | Less than 620
Financing Receivable
Purchased credit-impaired in accordance with ASC 310-30	12,422	13,088
Consumer | ≥ 620 but less than 660
Financing Receivable
Purchased credit-impaired in accordance with ASC 310-30	14,816	15,431
Consumer | Equal to or greater than 660
Financing Receivable
Purchased credit-impaired in accordance with ASC 310-30	167,078	172,145
Consumer | Government-guaranteed
Non-Accrual Details
Loans, past due	1,301	1,474
Consumer | 30 to 89 Days Past Due
Non-Accrual Details
Loans, past due	3,052	3,275
Consumer | Equal to greater than 90 days past due
Non-Accrual Details
Loans, past due	2,784	3,127
Consumer | Residential first mortgages
Non-Accrual Details
Loans at fair value	$ 27	$ 29
Number of days past due, non-accrual status	90 days	90 days
Consumer | Residential first mortgages | Less than or equal to 80%
Financing Receivable
Purchased credit-impaired in accordance with ASC 310-30	$ 44,740	$ 45,849
Consumer | Residential first mortgages | 80% but less than or equal to 100%
Financing Receivable
Purchased credit-impaired in accordance with ASC 310-30	2,820	3,467
Consumer | Residential first mortgages | Greater than 100%
Financing Receivable
Purchased credit-impaired in accordance with ASC 310-30	262	324
Consumer | Residential first mortgages | Less than 620
Financing Receivable
Purchased credit-impaired in accordance with ASC 310-30	2,392	2,744
Consumer | Residential first mortgages | ≥ 620 but less than 660
Financing Receivable
Purchased credit-impaired in accordance with ASC 310-30	2,195	2,422
Consumer | Residential first mortgages | Equal to or greater than 660
Financing Receivable
Purchased credit-impaired in accordance with ASC 310-30	43,056	44,279
Consumer | Home equity loans | Less than or equal to 80%
Financing Receivable
Purchased credit-impaired in accordance with ASC 310-30	12,177	12,869
Consumer | Home equity loans | 80% but less than or equal to 100%
Financing Receivable
Purchased credit-impaired in accordance with ASC 310-30	2,856	3,653
Consumer | Home equity loans | Greater than 100%
Financing Receivable
Purchased credit-impaired in accordance with ASC 310-30	937	1,305
Consumer | Home equity loans | Less than 620
Financing Receivable
Purchased credit-impaired in accordance with ASC 310-30	1,542	1,750
Consumer | Home equity loans | ≥ 620 but less than 660
Financing Receivable
Purchased credit-impaired in accordance with ASC 310-30	1,248	1,418
Consumer | Home equity loans | Equal to or greater than 660
Financing Receivable
Purchased credit-impaired in accordance with ASC 310-30	13,263	14,743
Consumer | Credit cards | Less than 620
Financing Receivable
Purchased credit-impaired in accordance with ASC 310-30	8,227	8,310
Consumer | Credit cards | ≥ 620 but less than 660
Financing Receivable
Purchased credit-impaired in accordance with ASC 310-30	11,120	11,320
Consumer | Credit cards | Equal to or greater than 660
Financing Receivable
Purchased credit-impaired in accordance with ASC 310-30	108,311	110,522
Consumer | Installment and other revolving | Less than 620
Financing Receivable
Purchased credit-impaired in accordance with ASC 310-30	261	284
Consumer | Installment and other revolving | ≥ 620 but less than 660
Financing Receivable
Purchased credit-impaired in accordance with ASC 310-30	253	271
Consumer | Installment and other revolving | Equal to or greater than 660
Financing Receivable
Purchased credit-impaired in accordance with ASC 310-30	$ 2,448	2,601
Consumer | Commercial banking
Non-Accrual Details
Number of days past due, non-accrual status	90 days
Consumer | Total GCB and Corporate/Other consumer
Non-Accrual Details
Loans, current	$ 318,122	317,184
Loans, net of unearned income	325,259	325,060
Total non-accrual	2,848	3,158
90 days past due and accruing	2,652	2,991
Consumer | Total GCB and Corporate/Other consumer | Government-guaranteed
Non-Accrual Details
Loans, past due	1,301	1,474
Consumer | Total GCB and Corporate/Other consumer | 30 to 89 Days Past Due
Non-Accrual Details
Loans, past due	3,052	3,275
Consumer | Total GCB and Corporate/Other consumer | Equal to greater than 90 days past due
Non-Accrual Details
Loans, past due	2,784	3,127
Consumer | Other
Non-Accrual Details
Loans, current	2	3
Loans, net of unearned income	2	3
Total non-accrual	0	0
90 days past due and accruing	0	0
Consumer | Other | Government-guaranteed
Non-Accrual Details
Loans, past due	0	0
Consumer | Other | 30 to 89 Days Past Due
Non-Accrual Details
Loans, past due	0	0
Consumer | Other | Equal to greater than 90 days past due
Non-Accrual Details
Loans, past due	0	0
Consumer | In North America offices
Non-Accrual Details
Loans, current	205,914	213,222
Loans, net of unearned income	211,310	219,491
Total non-accrual	1,754	2,160
90 days past due and accruing	2,398	2,752
Consumer | In North America offices | Government-guaranteed
Non-Accrual Details
Loans, past due	1,301	1,474
Consumer | In North America offices | 30 to 89 Days Past Due
Non-Accrual Details
Loans, past due	2,050	2,365
Consumer | In North America offices | Equal to greater than 90 days past due
Non-Accrual Details
Loans, past due	2,045	2,430
Consumer | In North America offices | Residential first mortgages
Non-Accrual Details
Loans, current	49,255	50,766
Loans, net of unearned income	51,254	53,133
Total non-accrual	654	848
90 days past due and accruing	1,035	1,227
Mortgage loans in process of foreclosure	100	100
Consumer | In North America offices | Residential first mortgages | Government-guaranteed
Non-Accrual Details
Loans, past due	1,301	1,474
Consumer | In North America offices | Residential first mortgages | 30 to 89 Days Past Due
Non-Accrual Details
Loans, past due	438	522
Consumer | In North America offices | Residential first mortgages | 30 to 89 Days Past Due | Government-guaranteed
Non-Accrual Details
Loans, past due	300	200
Consumer | In North America offices | Residential first mortgages | Equal to greater than 90 days past due
Non-Accrual Details
Loans, past due	260	371
Consumer | In North America offices | Residential first mortgages | Equal to greater than 90 days past due | Government-guaranteed
Non-Accrual Details
Loans, past due	1,000	1,300
Consumer | In North America offices | Home equity loans
Non-Accrual Details
Loans, current	15,862	18,767
Loans, net of unearned income	16,448	19,454
Total non-accrual	796	914
90 days past due and accruing	0	0
Home equity loans in process of foreclosure	100	100
Consumer | In North America offices | Home equity loans | Government-guaranteed
Non-Accrual Details
Loans, past due	0	0
Consumer | In North America offices | Home equity loans | 30 to 89 Days Past Due
Non-Accrual Details
Loans, past due	213	249
Consumer | In North America offices | Home equity loans | Equal to greater than 90 days past due
Non-Accrual Details
Loans, past due	373	438
Consumer | In North America offices | Credit cards
Non-Accrual Details
Loans, current	128,173	130,327
Loans, net of unearned income	130,874	133,301
Total non-accrual	0	0
90 days past due and accruing	1,352	1,509
Consumer | In North America offices | Credit cards | Government-guaranteed
Non-Accrual Details
Loans, past due	0	0
Consumer | In North America offices | Credit cards | 30 to 89 Days Past Due
Non-Accrual Details
Loans, past due	1,349	1,465
Consumer | In North America offices | Credit cards | Equal to greater than 90 days past due
Non-Accrual Details
Loans, past due	1,352	1,509
Consumer | In North America offices | Installment and other revolving
Non-Accrual Details
Loans, current	3,475	4,486
Loans, net of unearned income	3,531	4,630
Total non-accrual	19	70
90 days past due and accruing	0	2
Consumer | In North America offices | Installment and other revolving | Government-guaranteed
Non-Accrual Details
Loans, past due	0	0
Consumer | In North America offices | Installment and other revolving | 30 to 89 Days Past Due
Non-Accrual Details
Loans, past due	42	106
Consumer | In North America offices | Installment and other revolving | Equal to greater than 90 days past due
Non-Accrual Details
Loans, past due	14	38
Consumer | In North America offices | Commercial banking
Non-Accrual Details
Loans, current	9,149	8,876
Loans, net of unearned income	9,203	8,973
Total non-accrual	285	328
90 days past due and accruing	11	14
Consumer | In North America offices | Commercial banking | Government-guaranteed
Non-Accrual Details
Loans, past due	0	0
Consumer | In North America offices | Commercial banking | 30 to 89 Days Past Due
Non-Accrual Details
Loans, past due	8	23
Consumer | In North America offices | Commercial banking | Equal to greater than 90 days past due
Non-Accrual Details
Loans, past due	46	74
Consumer | In offices outside North America
Non-Accrual Details
Loans, current	112,208	103,962
Loans, net of unearned income	113,949	105,569
Total non-accrual	1,094	998
90 days past due and accruing	254	239
Consumer | In offices outside North America | Government-guaranteed
Non-Accrual Details
Loans, past due	0	0
Consumer | In offices outside North America | 30 to 89 Days Past Due
Non-Accrual Details
Loans, past due	1,002	910
Consumer | In offices outside North America | Equal to greater than 90 days past due
Non-Accrual Details
Loans, past due	739	697
Consumer | In offices outside North America | Residential first mortgages
Non-Accrual Details
Loans, current	36,813	35,862
Loans, net of unearned income	37,197	36,203
Total non-accrual	412	360
90 days past due and accruing	0	0
Consumer | In offices outside North America | Residential first mortgages | Government-guaranteed
Non-Accrual Details
Loans, past due	0	0
Consumer | In offices outside North America | Residential first mortgages | 30 to 89 Days Past Due
Non-Accrual Details
Loans, past due	227	206
Consumer | In offices outside North America | Residential first mortgages | Equal to greater than 90 days past due
Non-Accrual Details
Loans, past due	157	135
Consumer | In offices outside North America | Credit cards
Non-Accrual Details
Loans, current	23,985	22,363
Loans, net of unearned income	24,773	23,055
Total non-accrual	313	258
90 days past due and accruing	254	239
Consumer | In offices outside North America | Credit cards | Government-guaranteed
Non-Accrual Details
Loans, past due	0	0
Consumer | In offices outside North America | Credit cards | 30 to 89 Days Past Due
Non-Accrual Details
Loans, past due	418	368
Consumer | In offices outside North America | Credit cards | Equal to greater than 90 days past due
Non-Accrual Details
Loans, past due	370	324
Consumer | In offices outside North America | Installment and other revolving
Non-Accrual Details
Loans, current	24,760	22,683
Loans, net of unearned income	25,169	23,073
Total non-accrual	165	163
90 days past due and accruing	0	0
Consumer | In offices outside North America | Installment and other revolving | Government-guaranteed
Non-Accrual Details
Loans, past due	0	0
Consumer | In offices outside North America | Installment and other revolving | 30 to 89 Days Past Due
Non-Accrual Details
Loans, past due	281	264
Consumer | In offices outside North America | Installment and other revolving | Equal to greater than 90 days past due
Non-Accrual Details
Loans, past due	128	126
Consumer | In offices outside North America | Commercial banking
Non-Accrual Details
Loans, current	26,650	23,054
Loans, net of unearned income	26,810	23,238
Total non-accrual	204	217
90 days past due and accruing	0	0
Consumer | In offices outside North America | Commercial banking | Government-guaranteed
Non-Accrual Details
Loans, past due	0	0
Consumer | In offices outside North America | Commercial banking | 30 to 89 Days Past Due
Non-Accrual Details
Loans, past due	76	72
Consumer | In offices outside North America | Commercial banking | Equal to greater than 90 days past due
Non-Accrual Details
Loans, past due	$ 84	$ 112