SECURITIES - Schedule of Investments (Details) - USD ($) $ in Millions		Sep. 30, 2023	Dec. 31, 2022
Debt Securities, Available-for-Sale, Fair Value to Amortized Cost, after Allowance for Credit Loss [Abstract]
Fair Value	[1]	$ 25,069	$ 24,007
Debt Securities, Held-to-Maturity, Fair Value to Amortized Cost, after Allowance for Credit Loss [Abstract]
Amortized Cost	[1]	9,320	9,834
Gross Unrealized Gains		1	4
Gross Unrealized Gains		(1,267)	(796)
Fair Value		8,054	9,042
Total equity securities, at cost, Amortized Cost		995	1,058
Equity securities, at cost, fair value		995	1,058
Equity Securities, Amortized Cost		163	153
Equity Securities, Fair Value		163	153
Portfolio level basis adjustments excluded from amortized cost		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		28,204	26,458
Gross Unrealized Gains		1	11
Gross Unrealized Losses		(3,136)	(2,462)
Fair Value		25,069	24,007
U.S. Treasury and other
Debt Securities, Available-for-Sale, Fair Value to Amortized Cost, after Allowance for Credit Loss [Abstract]
Amortized Cost		4,025	3,678
Gross Unrealized Gains		0	1
Gross Unrealized Losses		(251)	(193)
Fair Value		3,774	3,486
State and political subdivisions
Debt Securities, Available-for-Sale, Fair Value to Amortized Cost, after Allowance for Credit Loss [Abstract]
Amortized Cost		2	2
Gross Unrealized Gains		0	0
Gross Unrealized Losses		0	0
Fair Value		2	2
Total mortgage-backed securities
Debt Securities, Available-for-Sale, Fair Value to Amortized Cost, after Allowance for Credit Loss [Abstract]
Amortized Cost		23,380	21,530
Gross Unrealized Gains		1	10
Gross Unrealized Losses		(2,877)	(2,227)
Fair Value		20,504	19,313
Debt Securities, Held-to-Maturity, Fair Value to Amortized Cost, after Allowance for Credit Loss [Abstract]
Amortized Cost		8,810	9,253
Gross Unrealized Gains		0	4
Gross Unrealized Gains		(1,241)	(751)
Fair Value		7,569	8,506
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		23,101	21,250
Gross Unrealized Gains		1	10
Gross Unrealized Losses		(2,845)	(2,198)
Fair Value		20,257	19,062
Debt Securities, Held-to-Maturity, Fair Value to Amortized Cost, after Allowance for Credit Loss [Abstract]
Amortized Cost		8,810	9,253
Gross Unrealized Gains		0	4
Gross Unrealized Gains		(1,241)	(751)
Fair Value		7,569	8,506
Other/non-agency
Debt Securities, Available-for-Sale, Fair Value to Amortized Cost, after Allowance for Credit Loss [Abstract]
Amortized Cost		279	280
Gross Unrealized Gains		0	0
Gross Unrealized Losses		(32)	(29)
Fair Value		247	251
Collateralized loan obligations
Debt Securities, Available-for-Sale, Fair Value to Amortized Cost, after Allowance for Credit Loss [Abstract]
Amortized Cost		797	1,248
Gross Unrealized Gains		0	0
Gross Unrealized Losses		(8)	(42)
Fair Value		789	1,206
Asset-backed securities
Debt Securities, Held-to-Maturity, Fair Value to Amortized Cost, after Allowance for Credit Loss [Abstract]
Amortized Cost		510	581
Gross Unrealized Gains		1	0
Gross Unrealized Gains		(26)	(45)
Fair Value		$ 485	$ 536

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