LOANS - Consumer Troubled Debt Restructurings (Details) - Consumer $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2017 USD ($) loan	Jun. 30, 2016 USD ($) loan	Jun. 30, 2017 USD ($) loan	Jun. 30, 2016 USD ($) loan	Dec. 31, 2016
Loans receivable
Period within which default occurred post-modification			1 year
Number of days past due, non-accrual status			60 days
Residential first mortgages
Loans receivable
Number of days past due, non-accrual status			90 days		90 days
Commercial banking
Loans receivable
Number of days past due, non-accrual status			90 days
In North America offices
Loans receivable
Number of loans modified | loan	54,843	46,374	116,072	99,217
Post-modification recorded investment	$ 422	$ 417	$ 845	$ 865
TDR in payment default	$ 115	$ 107	$ 228	$ 254
In North America offices | Residential first mortgages
Loans receivable
Number of loans modified | loan	806	1,346	1,772	2,814
Post-modification recorded investment	$ 116	$ 205	$ 246	$ 417
Average interest rate reduction	1.00%	1.00%	1.00%	1.00%
Post-modification recorded investment for borrowers that have gone through Chapter 7 bankruptcy	$ 15	$ 21	$ 30	$ 41
TDR in payment default	48	52	99	139
In North America offices | Residential first mortgages | New OCC guidance
Loans receivable
Post-modification recorded investment for borrowers that have gone through Chapter 7 bankruptcy	$ 11	$ 13	$ 21	$ 26
In North America offices | Home equity loans
Loans receivable
Number of loans modified | loan	677	814	1,356	1,672
Post-modification recorded investment	$ 58	$ 30	$ 114	$ 60
Average interest rate reduction	2.00%	3.00%	1.00%	3.00%
Post-modification recorded investment for borrowers that have gone through Chapter 7 bankruptcy	$ 5	$ 4	$ 11	$ 10
TDR in payment default	8	6	17	14
In North America offices | Home equity loans | New OCC guidance
Loans receivable
Post-modification recorded investment for borrowers that have gone through Chapter 7 bankruptcy	$ 4	$ 4	$ 10	$ 9
In North America offices | Credit cards
Loans receivable
Number of loans modified | loan	53,080	42,792	112,417	91,901
Post-modification recorded investment	$ 203	$ 164	$ 433	$ 353
Average interest rate reduction	17.00%	17.00%	17.00%	17.00%
TDR in payment default	$ 57	$ 46	$ 109	$ 95
In North America offices | Installment and other revolving
Loans receivable
Number of loans modified | loan	250	1,381	471	2,766
Post-modification recorded investment	$ 2	$ 12	$ 4	$ 24
Average interest rate reduction	5.00%	14.00%	5.00%	14.00%
TDR in payment default	$ 1	$ 2	$ 1	$ 4
In North America offices | Commercial banking
Loans receivable
Number of loans modified | loan	30	41	56	64
Post-modification recorded investment	$ 43	$ 6	$ 48	$ 11
Average interest rate reduction	0.00%	0.00%	0.00%	0.00%
TDR in payment default	$ 1	$ 1	$ 2	$ 2
In offices outside the U.S.
Loans receivable
Number of loans modified | loan	40,981	40,481	78,170	114,782
Post-modification recorded investment	$ 196	$ 191	$ 380	$ 443
TDR in payment default	$ 72	$ 70	$ 139	$ 141
In offices outside the U.S. | Residential first mortgages
Loans receivable
Number of loans modified | loan	755	613	1,368	1,032
Post-modification recorded investment	$ 28	$ 23	$ 54	$ 38
Average interest rate reduction	0.00%	1.00%	0.00%	1.00%
TDR in payment default	$ 3	$ 3	$ 5	$ 6
In offices outside the U.S. | Credit cards
Loans receivable
Number of loans modified | loan	28,551	28,628	53,788	80,835
Post-modification recorded investment	$ 98	$ 90	$ 183	$ 213
Average interest rate reduction	12.00%	12.00%	13.00%	12.00%
TDR in payment default	$ 46	$ 37	$ 88	$ 73
In offices outside the U.S. | Installment and other revolving
Loans receivable
Number of loans modified | loan	11,622	11,198	22,929	32,842
Post-modification recorded investment	$ 64	$ 58	$ 124	$ 140
Average interest rate reduction	9.00%	7.00%	7.00%	7.00%
TDR in payment default	$ 23	$ 24	$ 46	$ 47
In offices outside the U.S. | Commercial banking
Loans receivable
Number of loans modified | loan	53	42	85	73
Post-modification recorded investment	$ 6	$ 20	$ 19	$ 52
Average interest rate reduction	0.00%	0.00%	(1.00%)	0.00%
TDR in payment default	$ 0	$ 6	$ 0	$ 15
Deferred principal | In North America offices
Loans receivable
Post-modification recorded investment	6	1	12	3
Deferred principal | In North America offices | Residential first mortgages
Loans receivable
Post-modification recorded investment	1	1	4	3
Deferred principal | In North America offices | Home equity loans
Loans receivable
Post-modification recorded investment	5	0	8	0
Deferred principal | In North America offices | Credit cards
Loans receivable
Post-modification recorded investment	0	0	0	0
Deferred principal | In North America offices | Installment and other revolving
Loans receivable
Post-modification recorded investment	0	0	0	0
Deferred principal | In North America offices | Commercial banking
Loans receivable
Post-modification recorded investment	0	0	0	0
Deferred principal | In offices outside the U.S.
Loans receivable
Post-modification recorded investment	0	0	0	0
Deferred principal | In offices outside the U.S. | Residential first mortgages
Loans receivable
Post-modification recorded investment	0	0	0	0
Deferred principal | In offices outside the U.S. | Credit cards
Loans receivable
Post-modification recorded investment	0	0	0	0
Deferred principal | In offices outside the U.S. | Installment and other revolving
Loans receivable
Post-modification recorded investment	0	0	0	0
Deferred principal | In offices outside the U.S. | Commercial banking
Loans receivable
Post-modification recorded investment	0	0	0	0
Contingent principal forgiveness | In North America offices
Loans receivable
Post-modification recorded investment	0	0	0	0
Contingent principal forgiveness | In North America offices | Residential first mortgages
Loans receivable
Post-modification recorded investment	0	0	0	0
Contingent principal forgiveness | In North America offices | Home equity loans
Loans receivable
Post-modification recorded investment	0	0	0	0
Contingent principal forgiveness | In North America offices | Credit cards
Loans receivable
Post-modification recorded investment	0	0	0	0
Contingent principal forgiveness | In North America offices | Installment and other revolving
Loans receivable
Post-modification recorded investment	0	0	0	0
Contingent principal forgiveness | In North America offices | Commercial banking
Loans receivable
Post-modification recorded investment	0	0	0	0
Contingent principal forgiveness | In offices outside the U.S.
Loans receivable
Post-modification recorded investment	0	0	0	0
Contingent principal forgiveness | In offices outside the U.S. | Residential first mortgages
Loans receivable
Post-modification recorded investment	0	0	0	0
Contingent principal forgiveness | In offices outside the U.S. | Credit cards
Loans receivable
Post-modification recorded investment	0	0	0	0
Contingent principal forgiveness | In offices outside the U.S. | Installment and other revolving
Loans receivable
Post-modification recorded investment	0	0	0	0
Contingent principal forgiveness | In offices outside the U.S. | Commercial banking
Loans receivable
Post-modification recorded investment	0	0	0	0
Principal forgiveness | In North America offices
Loans receivable
Post-modification recorded investment	1	1	1	2
Principal forgiveness | In North America offices | Residential first mortgages
Loans receivable
Post-modification recorded investment	1	1	1	2
Principal forgiveness | In North America offices | Home equity loans
Loans receivable
Post-modification recorded investment	0	0	0	0
Principal forgiveness | In North America offices | Credit cards
Loans receivable
Post-modification recorded investment	0	0	0	0
Principal forgiveness | In North America offices | Installment and other revolving
Loans receivable
Post-modification recorded investment	0	0	0	0
Principal forgiveness | In North America offices | Commercial banking
Loans receivable
Post-modification recorded investment	0	0	0	0
Principal forgiveness | In offices outside the U.S.
Loans receivable
Post-modification recorded investment	4	4	10	8
Principal forgiveness | In offices outside the U.S. | Residential first mortgages
Loans receivable
Post-modification recorded investment	0	0	0	0
Principal forgiveness | In offices outside the U.S. | Credit cards
Loans receivable
Post-modification recorded investment	2	2	4	4
Principal forgiveness | In offices outside the U.S. | Installment and other revolving
Loans receivable
Post-modification recorded investment	2	2	6	4
Principal forgiveness | In offices outside the U.S. | Commercial banking
Loans receivable
Post-modification recorded investment	$ 0	$ 0	$ 0	$ 0