NONINTEREST INCOME - Components of Revenue from Contracts with Customers (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 307	$ 258	$ 902	$ 779
Total noninterest income	514	654	1,541	1,741
Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from other sources	207	396	639	962
Total noninterest income	514	654	1,541	1,741
Consumer Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	200	173	569	509
Consumer Banking \| Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from other sources	115	322	380	771
Total noninterest income	315	495	949	1,280
Commercial Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	107	85	333	270
Commercial Banking \| Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from other sources	61	59	183	143
Total noninterest income	168	144	516	413
Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Other \| Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from other sources	31	15	76	48
Total noninterest income	31	15	76	48
Service charges and fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	109	96	308	298
Service charges and fees \| Consumer Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	82	71	230	222
Service charges and fees \| Commercial Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	27	25	78	76
Service charges and fees \| Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Card fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	65	56	183	160
Card fees \| Consumer Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	57	49	160	136
Card fees \| Commercial Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	8	7	23	24
Card fees \| Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Capital markets fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	69	50	225	163
Capital markets fees \| Consumer Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Capital markets fees \| Commercial Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	69	50	225	163
Capital markets fees \| Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Trust and investment services fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	61	53	179	151
Trust and investment services fees \| Consumer Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	61	53	179	151
Trust and investment services fees \| Commercial Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Trust and investment services fees \| Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Other banking fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	3	3	7	7
Other banking fees \| Consumer Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Other banking fees \| Commercial Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	3	3	7	7
Other banking fees \| Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 0	$ 0	$ 0	$ 0

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The total amount of noninterest income which may be derived from: (1) fees and commissions; (2) premiums earned; (3) insurance policy charges; (4) the sale or disposal of assets; and (5) other sources not otherwise specified.

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Amount of revenue earned, classified as other, excluding interest income.

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Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

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