REVENUE FROM CONTRACTS WITH CUSTOMERS - Disaggregation by Segment (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2026	Mar. 31, 2025
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	$ 472	$ 351
Noninterest income within the scope of other GAAP topics	210	143
Noninterest income	682	494
Payments and cash management revenue
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	177	140
Wealth and asset management revenue
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	120	101
Customer deposit and loan fees
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	70	54
Capital markets and advisory fees
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	74	30
Noninterest income	132	67
Leasing revenue
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	3	4
Noninterest income	21	20
Leasing revenue
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	21	20
Noninterest income	13	14
Other noninterest income
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	7	2
Operating Segments \| Consumer & Regional Banking
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	329	278
Noninterest income within the scope of other GAAP topics	58	49
Noninterest income	387	327
Operating Segments \| Consumer & Regional Banking \| Payments and cash management revenue
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	120	108
Operating Segments \| Consumer & Regional Banking \| Wealth and asset management revenue
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	114	95
Operating Segments \| Consumer & Regional Banking \| Customer deposit and loan fees
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	66	52
Operating Segments \| Consumer & Regional Banking \| Capital markets and advisory fees
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	7	4
Operating Segments \| Consumer & Regional Banking \| Leasing revenue
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	2	1
Operating Segments \| Consumer & Regional Banking \| Leasing revenue
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	18	17
Operating Segments \| Consumer & Regional Banking \| Other noninterest income
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	2	1
Operating Segments \| Commercial Banking
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	143	73
Noninterest income within the scope of other GAAP topics	109	89
Noninterest income	252	162
Operating Segments \| Commercial Banking \| Payments and cash management revenue
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	57	32
Operating Segments \| Commercial Banking \| Wealth and asset management revenue
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	6	6
Operating Segments \| Commercial Banking \| Customer deposit and loan fees
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	4	2
Operating Segments \| Commercial Banking \| Capital markets and advisory fees
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	67	26
Operating Segments \| Commercial Banking \| Leasing revenue
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	1	3
Operating Segments \| Commercial Banking \| Leasing revenue
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	3	3
Operating Segments \| Commercial Banking \| Other noninterest income
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	5	1
Treasury / Other
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	0	0
Noninterest income within the scope of other GAAP topics	43	5
Noninterest income	43	5
Treasury / Other \| Payments and cash management revenue
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	0	0
Treasury / Other \| Wealth and asset management revenue
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	0	0
Treasury / Other \| Customer deposit and loan fees
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	0	0
Treasury / Other \| Capital markets and advisory fees
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	0	0
Treasury / Other \| Leasing revenue
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	0	0
Treasury / Other \| Leasing revenue
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	0	0
Treasury / Other \| Other noninterest income
Disaggregation of Revenue [Line Items]
Wealth and asset management revenue	$ 0	$ 0

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