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BASIS OF PRESENTATION (Details) $ in Millions	3 Months Ended			12 Months Ended
BASIS OF PRESENTATION (Details) $ in Millions	Jun. 30, 2026 USD ($)	Mar. 31, 2026 USD ($) state segment	Mar. 31, 2025 USD ($)	Dec. 31, 2025 USD ($)	Dec. 31, 2007 shares
Class of Stock [Line Items]
Number of states in which entity operates \| state		11
Number of reportable segments \| segment		7
Decrease in other assets		$ (73)	$ 71
Decrease in other liabilities		$ 115	$ 106
Change in Accounting Policy, Derivatives
Class of Stock [Line Items]
Decrease in loans and leases				$ 17
Decrease in other assets				283
Decrease in short-term borrowings				232
Decrease in other liabilities				$ 68
Visa Class B-1 Shares
Class of Stock [Line Items]
Number of shares received (in shares) \| shares					460,153
Visa Class B-1 Shares \| Subsequent Event \| Forecast
Class of Stock [Line Items]
Gain on sale of shares	$ 215