SECURITIES - Schedule of Investments (Details) - USD ($) $ in Millions		Mar. 31, 2026	Dec. 31, 2025
Debt Securities, Available-for-Sale, Fair Value to Amortized Cost, after Allowance for Credit Loss [Abstract]
Fair Value	[1]	$ 36,361	$ 35,697
Debt Securities, Held-to-Maturity, Fair Value to Amortized Cost, after Allowance for Credit Loss [Abstract]
Amortized Cost	[1]	7,800	7,933
Gross Unrealized Gains		1	2
Gross Unrealized Gains		(803)	(785)
Fair Value		6,998	7,150
Total equity securities, at cost, Amortized Cost		836	807
Equity securities, at cost, fair value		836	807
Equity Securities, Amortized Cost		336	317
Equity Securities, Fair Value		336	317
Portfolio level basis adjustments excluded from amortized cost		(4)	17
Total debt securities available for sale, at fair value
Debt Securities, Available-for-Sale, Fair Value to Amortized Cost, after Allowance for Credit Loss [Abstract]
Amortized Cost		37,726	36,900
Gross Unrealized Gains		140	225
Gross Unrealized Losses		(1,505)	(1,428)
Fair Value		36,361	35,697
U.S. Treasury and other
Debt Securities, Available-for-Sale, Fair Value to Amortized Cost, after Allowance for Credit Loss [Abstract]
Amortized Cost		4,385	3,163
Gross Unrealized Gains		6	10
Gross Unrealized Losses		(57)	(50)
Fair Value		4,334	3,123
State and political subdivisions
Debt Securities, Available-for-Sale, Fair Value to Amortized Cost, after Allowance for Credit Loss [Abstract]
Amortized Cost		1	1
Gross Unrealized Gains		0	0
Gross Unrealized Losses		0	0
Fair Value		1	1
Total mortgage-backed securities
Debt Securities, Available-for-Sale, Fair Value to Amortized Cost, after Allowance for Credit Loss [Abstract]
Amortized Cost		33,251	33,647
Gross Unrealized Gains		134	215
Gross Unrealized Losses		(1,448)	(1,378)
Fair Value		31,937	32,484
Debt Securities, Held-to-Maturity, Fair Value to Amortized Cost, after Allowance for Credit Loss [Abstract]
Amortized Cost		7,484	7,595
Gross Unrealized Gains		1	2
Gross Unrealized Gains		(801)	(785)
Fair Value		6,684	6,812
Federal agencies and U.S. government sponsored entities
Debt Securities, Available-for-Sale, Fair Value to Amortized Cost, after Allowance for Credit Loss [Abstract]
Amortized Cost		32,986	33,379
Gross Unrealized Gains		134	215
Gross Unrealized Losses		(1,445)	(1,374)
Fair Value		31,675	32,220
Debt Securities, Held-to-Maturity, Fair Value to Amortized Cost, after Allowance for Credit Loss [Abstract]
Amortized Cost		7,484	7,595
Gross Unrealized Gains		1	2
Gross Unrealized Gains		(801)	(785)
Fair Value		6,684	6,812
Other/non-agency
Debt Securities, Available-for-Sale, Fair Value to Amortized Cost, after Allowance for Credit Loss [Abstract]
Amortized Cost		265	268
Gross Unrealized Gains		0	0
Gross Unrealized Losses		(3)	(4)
Fair Value		262	264
Collateralized loan obligations
Debt Securities, Available-for-Sale, Fair Value to Amortized Cost, after Allowance for Credit Loss [Abstract]
Amortized Cost		89	89
Gross Unrealized Gains		0	0
Gross Unrealized Losses		0	0
Fair Value		89	89
Asset-backed securities
Debt Securities, Held-to-Maturity, Fair Value to Amortized Cost, after Allowance for Credit Loss [Abstract]
Amortized Cost		316	338
Gross Unrealized Gains		0	0
Gross Unrealized Gains		(2)	0
Fair Value		$ 314	$ 338

[1] Includes only collateral pledged by the Company where counterparties have the right to sell or pledge the collateral.