LOANS - Credit Quality Indicators (Details) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 645,960	$ 667,767
Total loans, net of unearned income	645,960	667,767
Consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	357,583	376,534
Total loans, net of unearned income	357,583	376,534
Consumer | 90 days or more past due
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	1,932	1,963
Total loans, net of unearned income	1,932	1,963
Consumer | In North America offices
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	278,689	263,687
Total loans, net of unearned income	278,689	263,687
Consumer | In North America offices | 90 days or more past due
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	1,641	1,542
Total loans, net of unearned income	1,641	1,542
Consumer | In North America offices | 90 days or more past due | Personal Banking and Wealth Management
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	33,900	35,300
Total loans, net of unearned income	33,900	35,300
Consumer | In offices outside North America
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	78,894	112,847
Total loans, net of unearned income	78,894	112,847
Consumer | In offices outside North America | 90 days or more past due
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	291	421
Total loans, net of unearned income	291	421
Consumer | In offices outside North America | 90 days or more past due | Personal Banking and Wealth Management
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	19,400	24,500
Total loans, net of unearned income	19,400	24,500
Consumer | Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	93,381	83,361
Total loans, net of unearned income	93,381	83,361
Consumer | Residential mortgages | In North America offices
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	93,381	83,361
Total loans, net of unearned income	93,381	83,361
Consumer | Residential mortgages | In North America offices | Global Wealth Management Business
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income		19,800
Total loans, net of unearned income		19,800
Consumer | Residential mortgages | In North America offices | 90 days or more past due
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	337	499
Total loans, net of unearned income	337	499
Consumer | Residential mortgages | In offices outside North America
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	27,281	37,889
Total loans, net of unearned income	27,281	37,889
Consumer | Residential mortgages | In offices outside North America | Global Wealth Management Business
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	19,300	19,800
Total loans, net of unearned income	19,300	19,800
Consumer | Residential mortgages | In offices outside North America | 90 days or more past due
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	86	158
Total loans, net of unearned income	86	158
Consumer | Credit cards
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	139,856	133,351
Total loans, net of unearned income	139,856	133,351
Consumer | Credit cards | CANADA
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	548	517
Total loans, net of unearned income	548	517
Consumer | Credit cards | In North America offices
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	140,404	133,868
Total loans, net of unearned income	140,404	133,868
Consumer | Credit cards | In North America offices | 90 days or more past due
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	1,105	871
Total loans, net of unearned income	1,105	871
Consumer | Credit cards | In offices outside North America
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	11,764	17,808
Total loans, net of unearned income	11,764	17,808
Consumer | Credit cards | In offices outside North America | 90 days or more past due
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	125	188
Total loans, net of unearned income	125	188
Consumer | Home equity loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	4,794	5,745
Total loans, net of unearned income	4,794	5,745
Consumer | Home equity loans | In North America offices
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	4,794	5,745
Total loans, net of unearned income	4,794	5,745
Consumer | Home equity loans | In North America offices | 90 days or more past due
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	139	156
Total loans, net of unearned income	139	156
Consumer | Personal, small business and other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	39,199	39,806
Total loans, net of unearned income	39,199	39,806
Consumer | Personal, small business and other | CANADA
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	911	907
Total loans, net of unearned income	911	907
Consumer | Personal, small business and other | In North America offices
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	40,110	40,713
Total loans, net of unearned income	40,110	40,713
Consumer | Personal, small business and other | In North America offices | Global Wealth Management Business
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	36,600	37,900
Total loans, net of unearned income	$ 36,600	$ 37,900
Consumer | Personal, small business and other | In North America offices | Global Wealth Management Business | Internal Investment Grade
Financing Receivable, Credit Quality Indicator [Line Items]
Percentage of loans rated investment grade	96.00%	95.00%
Consumer | Personal, small business and other | In North America offices | 90 days or more past due
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 60	$ 16
Total loans, net of unearned income	60	16
Consumer | Personal, small business and other | In offices outside North America
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	39,849	57,150
Total loans, net of unearned income	$ 39,849	$ 57,150
Consumer | Personal, small business and other | In offices outside North America | Internal Investment Grade
Financing Receivable, Credit Quality Indicator [Line Items]
Percentage of loans rated investment grade	96.00%	95.00%
Consumer | Personal, small business and other | In offices outside North America | Global Wealth Management Business
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 28,500	$ 34,600
Total loans, net of unearned income	$ 28,500	$ 34,600
Consumer | Personal, small business and other | In offices outside North America | Global Wealth Management Business | Internal Investment Grade
Financing Receivable, Credit Quality Indicator [Line Items]
Percentage of loans rated investment grade	94.00%	94.00%
Consumer | Personal, small business and other | In offices outside North America | 90 days or more past due
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 80	$ 75
Total loans, net of unearned income	80	75
Consumer | Less than or equal to 80%
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	91,936	83,339
Total loans, net of unearned income	91,936	83,339
Consumer | Less than or equal to 80% | Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	87,387	77,951
Current fiscal year	14,631	18,107
One year prior to current fiscal year	19,790	18,715
Two years prior to current fiscal year	17,274	10,047
Three years prior to current fiscal year	8,948	4,117
Four years prior to current fiscal year	3,667	4,804
Prior	23,077	22,161
Total loans, net of unearned income	87,387	77,951
Consumer | Less than or equal to 80% | Residential mortgages | In offices outside North America
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	24,625	36,281
Current fiscal year	2,347	6,334
One year prior to current fiscal year	4,316	5,996
Two years prior to current fiscal year	3,653	5,293
Three years prior to current fiscal year	3,243	3,729
Four years prior to current fiscal year	2,193	2,739
Prior	8,873	12,190
Total loans, net of unearned income	$ 24,625	$ 36,281
Loan to value ratio	49.00%	46.00%
Consumer | Less than or equal to 80% | Home equity loans (pre-reset)
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 2,278	$ 2,637
Total loans, net of unearned income	2,278	2,637
Consumer | Less than or equal to 80% | Home equity loans (post-reset)
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	2,271	2,751
Total loans, net of unearned income	2,271	2,751
Consumer | Less than or equal to 80% | Home equity loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	4,549	5,388
Total loans, net of unearned income	4,549	5,388
Consumer | Greater than 80% but less than or equal to 100%
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	4,886	3,903
Total loans, net of unearned income	4,886	3,903
Consumer | Greater than 80% but less than or equal to 100% | Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	4,836	3,805
Current fiscal year	3,653	2,723
One year prior to current fiscal year	737	446
Two years prior to current fiscal year	138	269
Three years prior to current fiscal year	111	136
Four years prior to current fiscal year	67	103
Prior	130	128
Total loans, net of unearned income	4,836	3,805
Consumer | Greater than 80% but less than or equal to 100% | Residential mortgages | In offices outside North America
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	2,386	1,569
Current fiscal year	865	989
One year prior to current fiscal year	1,076	292
Two years prior to current fiscal year	342	116
Three years prior to current fiscal year	62	32
Four years prior to current fiscal year	7	38
Prior	34	102
Total loans, net of unearned income	2,386	1,569
Consumer | Greater than 80% but less than or equal to 100% | Home equity loans (pre-reset)
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	28	46
Total loans, net of unearned income	28	46
Consumer | Greater than 80% but less than or equal to 100% | Home equity loans (post-reset)
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	22	52
Total loans, net of unearned income	22	52
Consumer | Greater than 80% but less than or equal to 100% | Home equity loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	50	98
Total loans, net of unearned income	50	98
Consumer | Greater than 100%
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	239	193
Total loans, net of unearned income	239	193
Consumer | Greater than 100% | Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	150	92
Current fiscal year	3	34
One year prior to current fiscal year	31	0
Two years prior to current fiscal year	0	29
Three years prior to current fiscal year	26	11
Four years prior to current fiscal year	8	4
Prior	82	14
Total loans, net of unearned income	150	92
Consumer | Greater than 100% | Residential mortgages | In offices outside North America
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	12	15
Current fiscal year	0	0
One year prior to current fiscal year	3	0
Two years prior to current fiscal year	0	1
Three years prior to current fiscal year	1	0
Four years prior to current fiscal year	0	0
Prior	8	14
Total loans, net of unearned income	12	15
Consumer | Greater than 100% | Home equity loans (pre-reset)
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	58	69
Total loans, net of unearned income	58	69
Consumer | Greater than 100% | Home equity loans (post-reset)
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	31	32
Total loans, net of unearned income	31	32
Consumer | Greater than 100% | Home equity loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	89	101
Total loans, net of unearned income	89	101
Consumer | LTV not available
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	1,114	1,671
Total loans, net of unearned income	1,114	1,671
Consumer | LTV not available | Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	1,008	1,513
Total loans, net of unearned income	1,008	1,513
Consumer | LTV not available | Residential mortgages | In offices outside North America
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	258	24
Total loans, net of unearned income	258	24
Consumer | LTV not available | Home equity loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	106	158
Total loans, net of unearned income	106	158
Consumer | Total
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	98,175	89,106
Total loans, net of unearned income	98,175	89,106
Consumer | Classifiably Managed and Delinquency Managed | In offices outside North America
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	80,400	114,300
Total loans, net of unearned income	80,400	114,300
Consumer | Classifiably Managed and Delinquency Managed | Personal, small business and other | In offices outside North America | Global Wealth Management Business
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	28,500	34,600
Total loans, net of unearned income	28,500	34,600
Consumer | Less than 680
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	31,598	28,598
Total loans, net of unearned income	31,598	28,598
Consumer | Less than 680 | Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	4,251	4,297
Current fiscal year	504	626
One year prior to current fiscal year	628	508
Two years prior to current fiscal year	472	373
Three years prior to current fiscal year	302	394
Four years prior to current fiscal year	302	343
Prior	2,043	2,053
Total loans, net of unearned income	4,251	4,297
Consumer | Less than 680 | Credit cards
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	26,172	23,115
Total loans, net of unearned income	26,172	23,115
Consumer | Less than 680 | Home equity loans (pre-reset)
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	237	263
Total loans, net of unearned income	237	263
Consumer | Less than 680 | Home equity loans (post-reset)
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	496	639
Total loans, net of unearned income	496	639
Consumer | Less than 680 | Home equity loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	733	902
Total loans, net of unearned income	733	902
Consumer | Less than 680 | Personal, small business and other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	442	284
Current fiscal year	162	59
One year prior to current fiscal year	99	22
Two years prior to current fiscal year	17	42
Three years prior to current fiscal year	25	34
Four years prior to current fiscal year	15	7
Prior	124	120
Total loans, net of unearned income	442	284
Consumer | 680 to 760
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	85,475	79,581
Total loans, net of unearned income	85,475	79,581
Consumer | 680 to 760 | Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	27,455	24,080
Current fiscal year	6,083	6,729
One year prior to current fiscal year	6,029	5,102
Two years prior to current fiscal year	4,806	3,074
Three years prior to current fiscal year	2,673	1,180
Four years prior to current fiscal year	1,110	1,455
Prior	6,754	6,540
Total loans, net of unearned income	27,455	24,080
Consumer | 680 to 760 | Credit cards
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	55,368	52,907
Total loans, net of unearned income	55,368	52,907
Consumer | 680 to 760 | Home equity loans (pre-reset)
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	913	1,030
Total loans, net of unearned income	913	1,030
Consumer | 680 to 760 | Home equity loans (post-reset)
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	890	1,047
Total loans, net of unearned income	890	1,047
Consumer | 680 to 760 | Home equity loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	1,803	2,077
Total loans, net of unearned income	1,803	2,077
Consumer | 680 to 760 | Personal, small business and other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	849	517
Current fiscal year	397	201
One year prior to current fiscal year	194	41
Two years prior to current fiscal year	24	53
Three years prior to current fiscal year	29	35
Four years prior to current fiscal year	15	8
Prior	190	179
Total loans, net of unearned income	849	517
Consumer | Greater than 760
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	114,751	106,515
Total loans, net of unearned income	114,751	106,515
Consumer | Greater than 760 | Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	54,918	48,039
Current fiscal year	10,880	12,349
One year prior to current fiscal year	12,782	12,153
Two years prior to current fiscal year	10,893	6,167
Three years prior to current fiscal year	5,424	2,216
Four years prior to current fiscal year	1,908	2,568
Prior	13,031	12,586
Total loans, net of unearned income	54,918	48,039
Consumer | Greater than 760 | Credit cards
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	56,529	55,137
Total loans, net of unearned income	56,529	55,137
Consumer | Greater than 760 | Home equity loans (pre-reset)
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	1,280	1,539
Total loans, net of unearned income	1,280	1,539
Consumer | Greater than 760 | Home equity loans (post-reset)
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	948	1,160
Total loans, net of unearned income	948	1,160
Consumer | Greater than 760 | Home equity loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	2,228	2,699
Total loans, net of unearned income	2,228	2,699
Consumer | Greater than 760 | Personal, small business and other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	1,076	640
Current fiscal year	594	319
One year prior to current fiscal year	250	64
Two years prior to current fiscal year	36	68
Three years prior to current fiscal year	36	37
Four years prior to current fiscal year	15	9
Prior	145	143
Total loans, net of unearned income	1,076	640
Consumer | FICO not available
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	11,496	12,245
Total loans, net of unearned income	11,496	12,245
Consumer | FICO not available | Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	6,757	6,945
Total loans, net of unearned income	6,757	6,945
Consumer | FICO not available | Credit cards
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	1,787	2,192
Total loans, net of unearned income	1,787	2,192
Consumer | FICO not available | Home equity loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	30	67
Total loans, net of unearned income	30	67
Consumer | FICO not available | Personal, small business and other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	2,922	3,041
Total loans, net of unearned income	2,922	3,041
Consumer | Classifiably Managed
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	33,910	35,324
Total loans, net of unearned income	33,910	35,324
Consumer | Classifiably Managed | In offices outside North America
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	19,432	24,482
Total loans, net of unearned income	19,432	24,482
Consumer | Classifiably Managed | Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	0	0
Total loans, net of unearned income	0	0
Consumer | Classifiably Managed | Residential mortgages | In offices outside North America
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	0	0
Total loans, net of unearned income	0	0
Consumer | Classifiably Managed | Credit cards
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	0	0
Total loans, net of unearned income	0	0
Consumer | Classifiably Managed | Credit cards | In offices outside North America
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	0	0
Total loans, net of unearned income	0	0
Consumer | Classifiably Managed | Home equity loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	0	0
Total loans, net of unearned income	0	0
Consumer | Classifiably Managed | Personal, small business and other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	33,910	35,324
Total loans, net of unearned income	33,910	35,324
Consumer | Classifiably Managed | Personal, small business and other | In North America offices | Global Wealth Management Business
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	33,900	35,300
Total loans, net of unearned income	33,900	35,300
Consumer | Classifiably Managed | Personal, small business and other | In offices outside North America
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	19,432	24,482
Total loans, net of unearned income	19,432	24,482
Consumer | Classifiably Managed | Personal, small business and other | In offices outside North America | Global Wealth Management Business
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	19,400	24,500
Total loans, net of unearned income	19,400	24,500
Consumer | Total loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	277,230	262,263
Total loans, net of unearned income	$ 277,230	$ 262,263