SECURITIES - Schedule of Investments (Details) - USD ($) $ in Millions		Jun. 30, 2023	Dec. 31, 2022
Debt Securities, Available-for-Sale, Fair Value to Amortized Cost, after Allowance for Credit Loss [Abstract]
Fair Value	[1]	$ 24,755	$ 24,007
Debt Securities, Held-to-Maturity, Fair Value to Amortized Cost, after Allowance for Credit Loss [Abstract]
Amortized Cost	[1]	9,520	9,834
Gross Unrealized Gains		6	4
Gross Unrealized Gains		(798)	(796)
Fair Value		8,728	9,042
Total equity securities, at cost, Amortized Cost		917	1,058
Equity securities, at cost, fair value		917	1,058
Equity Securities, Amortized Cost		147	153
Equity Securities, Fair Value		147	153
Portfolio level basis adjustments excluded from amortized cost		9
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		27,112	26,458
Gross Unrealized Gains		4	11
Gross Unrealized Losses		(2,361)	(2,462)
Fair Value		24,755	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		3,429	3,678
Gross Unrealized Gains		0	1
Gross Unrealized Losses		(193)	(193)
Fair Value		3,236	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		22,433	21,530
Gross Unrealized Gains		4	10
Gross Unrealized Losses		(2,148)	(2,227)
Fair Value		20,289	19,313
Debt Securities, Held-to-Maturity, Fair Value to Amortized Cost, after Allowance for Credit Loss [Abstract]
Amortized Cost		8,990	9,253
Gross Unrealized Gains		4	4
Gross Unrealized Gains		(769)	(751)
Fair Value		8,225	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		22,154	21,250
Gross Unrealized Gains		4	10
Gross Unrealized Losses		(2,116)	(2,198)
Fair Value		20,042	19,062
Debt Securities, Held-to-Maturity, Fair Value to Amortized Cost, after Allowance for Credit Loss [Abstract]
Amortized Cost		8,990	9,253
Gross Unrealized Gains		4	4
Gross Unrealized Gains		(769)	(751)
Fair Value		8,225	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		1,248	1,248
Gross Unrealized Gains		0	0
Gross Unrealized Losses		(20)	(42)
Fair Value		1,228	1,206
Asset-backed securities
Debt Securities, Held-to-Maturity, Fair Value to Amortized Cost, after Allowance for Credit Loss [Abstract]
Amortized Cost		530	581
Gross Unrealized Gains		2	0
Gross Unrealized Gains		(29)	(45)
Fair Value		$ 503	$ 536

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