LOANS - Consumer Troubled Debt Restructurings (Details) - Consumer $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015 USD ($) loan	Sep. 30, 2014 USD ($) loan	Sep. 30, 2015 USD ($) loan	Sep. 30, 2014 USD ($) loan	Dec. 31, 2014
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
Home equity loans
Loans receivable
Number of days past due, non-accrual status			90 days
Credit cards
Loans receivable
Number of days past due, non-accrual status			180 days
Installment and other
Loans receivable
Number of days past due, non-accrual status			90 days
Commercial market loans
Loans receivable
Number of days past due, non-accrual status			90 days
In North America Offices
Loans receivable
Number of loans modified | loan	49,399	67,074	155,141	194,261
Post-modification recorded investment	$ 546	$ 1,005	$ 1,852	$ 2,991
Deferred principal	2	16	8	46
Contingent principal forgiveness	1	11	3	30
Principal forgiveness	7	4	26	21
Loans in default	$ 160	$ 239	$ 509	$ 839
In North America Offices | Residential first mortgages
Loans receivable
Number of loans modified | loan	2,282	4,933	8,084	15,435
Post-modification recorded investment	$ 305	$ 626	$ 1,078	$ 1,866
Deferred principal	2	15	7	43
Contingent principal forgiveness	1	11	3	30
Principal forgiveness	$ 7	$ 1	$ 23	$ 7
Average interest rate reduction (as a percent)	1.00%	1.00%	1.00%	1.00%
Post-modification recorded investment for borrowers that have gone through Chapter 7 bankruptcy	$ 54	$ 74	$ 181	$ 240
Loans in default	101	149	329	562
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	$ 34	$ 45	$ 107	$ 144
In North America Offices | Home equity loans
Loans receivable
Number of loans modified | loan	1,021	1,900	3,571	6,102
Post-modification recorded investment	$ 36	$ 76	$ 126	$ 228
Deferred principal	0	1	1	3
Contingent principal forgiveness	0	0	0	0
Principal forgiveness	$ 0	$ 2	$ 3	$ 13
Average interest rate reduction (as a percent)	2.00%	3.00%	2.00%	2.00%
Post-modification recorded investment for borrowers that have gone through Chapter 7 bankruptcy	$ 17	$ 22	$ 46	$ 65
Loans in default	9	16	30	55
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	$ 14	$ 19	$ 39	$ 56
In North America Offices | Credit cards
Loans receivable
Number of loans modified | loan	44,972	48,775	140,130	136,501
Post-modification recorded investment	$ 186	$ 211	$ 582	$ 601
Deferred principal	0	0	0	0
Contingent principal forgiveness	0	0	0	0
Principal forgiveness	$ 0	$ 0	$ 0	$ 0
Average interest rate reduction (as a percent)	16.00%	16.00%	16.00%	15.00%
Loans in default	$ 47	$ 47	$ 139	$ 146
In North America Offices | Installment and other
Loans receivable
Number of loans modified | loan	1,035	11,420	3,111	36,086
Post-modification recorded investment	$ 9	$ 87	$ 27	$ 269
Deferred principal	0	0	0	0
Contingent principal forgiveness	0	0	0	0
Principal forgiveness	$ 0	$ 0	$ 0	$ 0
Average interest rate reduction (as a percent)	13.00%	6.00%	13.00%	6.00%
Loans in default	$ 2	$ 26	$ 6	$ 68
In North America Offices | Commercial market loans
Loans receivable
Number of loans modified | loan	89	46	245	137
Post-modification recorded investment	$ 10	$ 5	$ 39	$ 27
Deferred principal	0	0	0	0
Contingent principal forgiveness	0	0	0	0
Principal forgiveness	$ 0	$ 1	$ 0	$ 1
Average interest rate reduction (as a percent)	0.00%	0.00%	0.00%	0.00%
Loans in default	$ 1	$ 1	$ 5	$ 8
In offices outside the U.S.
Loans receivable
Number of loans modified | loan	53,421	56,452	162,330	155,952
Post-modification recorded investment	$ 207	$ 250	$ 640	$ 819
Deferred principal	0	0	0	0
Contingent principal forgiveness	0	0	0	0
Principal forgiveness	3	4	10	13
Loans in default	$ 66	$ 85	$ 207	$ 374
In offices outside the U.S. | Residential first mortgages
Loans receivable
Number of loans modified | loan	1,309	841	2,920	2,133
Post-modification recorded investment	$ 28	$ 30	$ 73	$ 79
Deferred principal	0	0	0	0
Contingent principal forgiveness	0	0	0	0
Principal forgiveness	$ 0	$ 0	$ 0	$ 1
Average interest rate reduction (as a percent)	0.00%	0.00%	0.00%	1.00%
Loans in default	$ 5	$ 6	$ 17	$ 16
In offices outside the U.S. | Home equity loans
Loans receivable
Number of loans modified | loan	13	15	43	53
Post-modification recorded investment	$ 2	$ 3	$ 7	$ 9
Deferred principal	0	0	0	0
Contingent principal forgiveness	0	0	0	0
Principal forgiveness	$ 0	$ 0	$ 0	$ 0
Average interest rate reduction (as a percent)	0.00%	0.00%	0.00%	0.00%
Loans in default	$ 0	$ 0	$ 0	$ 0
In offices outside the U.S. | Credit cards
Loans receivable
Number of loans modified | loan	32,774	40,468	110,792	109,337
Post-modification recorded investment	$ 87	$ 122	$ 288	$ 356
Deferred principal	0	0	0	0
Contingent principal forgiveness	0	0	0	0
Principal forgiveness	$ 2	$ 2	$ 5	$ 7
Average interest rate reduction (as a percent)	13.00%	12.00%	13.00%	13.00%
Loans in default	$ 34	$ 52	$ 106	$ 175
In offices outside the U.S. | Installment and other
Loans receivable
Number of loans modified | loan	19,283	15,077	48,397	44,158
Post-modification recorded investment	$ 76	$ 73	$ 207	$ 219
Deferred principal	0	0	0	0
Contingent principal forgiveness	0	0	0	0
Principal forgiveness	$ 1	$ 2	$ 5	$ 5
Average interest rate reduction (as a percent)	5.00%	8.00%	5.00%	9.00%
Loans in default	$ 20	$ 25	$ 66	$ 81
In offices outside the U.S. | Commercial market loans
Loans receivable
Number of loans modified | loan	42	51	178	271
Post-modification recorded investment	$ 14	$ 22	$ 65	$ 156
Deferred principal	0	0	0	0
Contingent principal forgiveness	0	0	0	0
Principal forgiveness	$ 0	$ 0	$ 0	$ 0
Average interest rate reduction (as a percent)	0.00%	0.00%	1.00%	0.00%
Loans in default	$ 7	$ 2	$ 18	$ 102