NONINTEREST INCOME - Components of Revenue from Contracts with Customers (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 1,325	$ 1,080	$ 1,172
Total noninterest income	2,135	2,319	1,877
Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from other sources	810	1,239	705
Total noninterest income	2,135	2,319	1,877
Consumer Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	757	690	818
Consumer Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from other sources	466	965	338
Total noninterest income	1,223	1,655	1,156
Commercial Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	568	390	354
Commercial Banking | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from other sources	241	205	253
Total noninterest income	809	595	607
Other Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0
Other Segments | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue from other sources	103	69	114
Total noninterest income	103	69	114
Service charges and fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	407	401	503
Service charges and fees | Consumer Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	302	301	400
Service charges and fees | Commercial Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	105	100	103
Service charges and fees | Other Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0
Card fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	248	216	254
Card fees | Consumer Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	216	185	215
Card fees | Commercial Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	32	31	39
Card fees | Other Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0
Capital markets fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	419	249	202
Capital markets fees | Consumer Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0
Capital markets fees | Commercial Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	419	249	202
Capital markets fees | Other Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0
Trust and investment services fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	239	203	202
Trust and investment services fees | Consumer Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	239	203	202
Trust and investment services fees | Commercial Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0
Trust and investment services fees | Other Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0
Other banking fees
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	12	11	11
Other banking fees | Consumer Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	1	1
Other banking fees | Commercial Banking
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	12	10	10
Other banking fees | Other Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 0	$ 0	$ 0