SECURITIES - Schedule of Investments (Details) - USD ($) $ in Millions		Sep. 30, 2025	Dec. 31, 2024
Debt Securities, Available-for-Sale, Fair Value to Amortized Cost, after Allowance for Credit Loss [Abstract]
Fair Value	[1]	$ 35,419	$ 32,765
Debt Securities, Held-to-Maturity, Fair Value to Amortized Cost, after Allowance for Credit Loss [Abstract]
Amortized Cost	[1]	8,124	8,599
Gross Unrealized Gains		1	1
Gross Unrealized Gains		(830)	(1,060)
Fair Value		7,295	7,540
Total equity securities, at cost, Amortized Cost		710	710
Equity securities, at cost, fair value		710	710
Equity Securities, Amortized Cost		286	220
Equity Securities, Fair Value		286	220
Portfolio level basis adjustments excluded from amortized cost		37	(75)
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		36,787	34,986
Gross Unrealized Gains		183	36
Gross Unrealized Losses		(1,551)	(2,257)
Fair Value		35,419	32,765
U.S. Treasury and other
Debt Securities, Available-for-Sale, Fair Value to Amortized Cost, after Allowance for Credit Loss [Abstract]
Amortized Cost		4,563	3,631
Gross Unrealized Gains		23	3
Gross Unrealized Losses		(72)	(109)
Fair Value		4,514	3,525
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		32,133	31,170
Gross Unrealized Gains		160	33
Gross Unrealized Losses		(1,479)	(2,148)
Fair Value		30,814	29,055
Debt Securities, Held-to-Maturity, Fair Value to Amortized Cost, after Allowance for Credit Loss [Abstract]
Amortized Cost		7,767	8,187
Gross Unrealized Gains		1	0
Gross Unrealized Gains		(830)	(1,051)
Fair Value		6,938	7,136
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		31,865	30,897
Gross Unrealized Gains		160	33
Gross Unrealized Losses		(1,474)	(2,135)
Fair Value		30,551	28,795
Debt Securities, Held-to-Maturity, Fair Value to Amortized Cost, after Allowance for Credit Loss [Abstract]
Amortized Cost		7,767	8,187
Gross Unrealized Gains		1	0
Gross Unrealized Gains		(830)	(1,051)
Fair Value		6,938	7,136
Other/non-agency
Debt Securities, Available-for-Sale, Fair Value to Amortized Cost, after Allowance for Credit Loss [Abstract]
Amortized Cost		268	273
Gross Unrealized Gains		0	0
Gross Unrealized Losses		(5)	(13)
Fair Value		263	260
Collateralized loan obligations
Debt Securities, Available-for-Sale, Fair Value to Amortized Cost, after Allowance for Credit Loss [Abstract]
Amortized Cost		90	184
Gross Unrealized Gains		0	0
Gross Unrealized Losses		0	0
Fair Value		90	184
Asset-backed securities
Debt Securities, Held-to-Maturity, Fair Value to Amortized Cost, after Allowance for Credit Loss [Abstract]
Amortized Cost		357	412
Gross Unrealized Gains		0	1
Gross Unrealized Gains		0	(9)
Fair Value		$ 357	$ 404

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