FAIR VALUES OF ASSETS AND LIABILITIES - Recurring Basis (Details) - USD ($) $ in Millions		Sep. 30, 2025	Dec. 31, 2024
Assets measured at fair value on a recurring basis
Trading account securities		$ 81	$ 53
Available-for-sale securities		26,085	27,273
Loans held for sale		817	652
Loans Accounted for Under FVO		171	173
Gross amounts of recognized assets		502	610
Derivative assets netting		(291)	(344)
Net amounts of assets presented in the condensed consolidated balance sheets		211	266
Short-term borrowings		252	199
Liabilities measured at fair value on a recurring basis
Long-term debt	[1]	17,315	16,374
Gross amounts of recognized liabilities		508	668
Gross amounts offset in the unaudited consolidated balance sheets		(163)	(90)
Derivative liabilities		345	578
U.S. Treasury
Assets measured at fair value on a recurring basis
Available-for-sale securities		5,410	6,556
Residential MBS
Assets measured at fair value on a recurring basis
Available-for-sale securities		9,675	10,017
Commercial MBS
Assets measured at fair value on a recurring basis
Available-for-sale securities		1,782	1,752
Other agencies
Assets measured at fair value on a recurring basis
Available-for-sale securities		113	130
Municipal securities
Assets measured at fair value on a recurring basis
Available-for-sale securities		4,115	3,988
Corporate debt
Assets measured at fair value on a recurring basis
Available-for-sale securities		175	109
Asset-backed securities
Assets measured at fair value on a recurring basis
Available-for-sale securities		259	311
Private-label CMO
Assets measured at fair value on a recurring basis
Available-for-sale securities		104	1,055
Fair Value, Recurring
Assets measured at fair value on a recurring basis
Trading account securities		81	53
Available-for-sale securities		26,085	27,273
Other securities		32	31
Loans held for sale		817	652
Loans Accounted for Under FVO		171	173
MSRs		576	573
Gross amounts of recognized assets			266
Derivative assets netting		(291)	(344)
Net amounts of assets presented in the condensed consolidated balance sheets		211
Assets held in trust for deferred compensation plans		211	191
Short-term borrowings		69
Liabilities measured at fair value on a recurring basis
Long-term debt		1,299	821
Gross amounts of recognized liabilities			578
Gross amounts offset in the unaudited consolidated balance sheets		(163)	(90)
Derivative liabilities		345
Fair Value, Recurring | U.S. Treasury
Assets measured at fair value on a recurring basis
Available-for-sale securities		5,410	6,556
Fair Value, Recurring | Residential MBS
Assets measured at fair value on a recurring basis
Available-for-sale securities		9,675	10,017
Fair Value, Recurring | Residential CMO
Assets measured at fair value on a recurring basis
Available-for-sale securities		4,442	3,345
Fair Value, Recurring | Commercial MBS
Assets measured at fair value on a recurring basis
Available-for-sale securities		1,782	1,752
Fair Value, Recurring | Other agencies
Assets measured at fair value on a recurring basis
Available-for-sale securities		113	130
Fair Value, Recurring | Municipal securities
Assets measured at fair value on a recurring basis
Available-for-sale securities		4,115	3,988
Fair Value, Recurring | Corporate debt
Assets measured at fair value on a recurring basis
Available-for-sale securities		175	1,055
Fair Value, Recurring | Asset-backed securities
Assets measured at fair value on a recurring basis
Available-for-sale securities		259	311
Fair Value, Recurring | Private-label CMO
Assets measured at fair value on a recurring basis
Available-for-sale securities		104	109
Fair Value, Recurring | Other securities/sovereign debt
Assets measured at fair value on a recurring basis
Available-for-sale securities		10	10
Fair Value, Recurring | Level 1
Assets measured at fair value on a recurring basis
Trading account securities		2	1
Available-for-sale securities		5,410	6,556
Other securities		30	29
Loans held for sale		0	0
Loans Accounted for Under FVO		0	0
MSRs		0	0
Gross amounts of recognized assets		0	0
Assets held in trust for deferred compensation plans		211	191
Short-term borrowings		57
Liabilities measured at fair value on a recurring basis
Long-term debt		0	0
Gross amounts of recognized liabilities		0	0
Fair Value, Recurring | Level 1 | U.S. Treasury
Assets measured at fair value on a recurring basis
Available-for-sale securities		5,410	6,556
Fair Value, Recurring | Level 1 | Residential MBS
Assets measured at fair value on a recurring basis
Available-for-sale securities		0	0
Fair Value, Recurring | Level 1 | Residential CMO
Assets measured at fair value on a recurring basis
Available-for-sale securities		0	0
Fair Value, Recurring | Level 1 | Commercial MBS
Assets measured at fair value on a recurring basis
Available-for-sale securities		0	0
Fair Value, Recurring | Level 1 | Other agencies
Assets measured at fair value on a recurring basis
Available-for-sale securities		0	0
Fair Value, Recurring | Level 1 | Municipal securities
Assets measured at fair value on a recurring basis
Available-for-sale securities		0	0
Fair Value, Recurring | Level 1 | Corporate debt
Assets measured at fair value on a recurring basis
Available-for-sale securities		0	0
Fair Value, Recurring | Level 1 | Asset-backed securities
Assets measured at fair value on a recurring basis
Available-for-sale securities		0	0
Fair Value, Recurring | Level 1 | Private-label CMO
Assets measured at fair value on a recurring basis
Available-for-sale securities		0	0
Fair Value, Recurring | Level 1 | Other securities/sovereign debt
Assets measured at fair value on a recurring basis
Available-for-sale securities		0	0
Fair Value, Recurring | Level 2
Assets measured at fair value on a recurring basis
Trading account securities		79	52
Available-for-sale securities		16,524	16,693
Other securities		2	2
Loans held for sale		817	652
Loans Accounted for Under FVO		108	112
MSRs		0	0
Gross amounts of recognized assets		493	606
Assets held in trust for deferred compensation plans		0	0
Short-term borrowings		12
Liabilities measured at fair value on a recurring basis
Long-term debt		1,299	821
Gross amounts of recognized liabilities		502	666
Fair Value, Recurring | Level 2 | U.S. Treasury
Assets measured at fair value on a recurring basis
Available-for-sale securities		0	0
Fair Value, Recurring | Level 2 | Residential MBS
Assets measured at fair value on a recurring basis
Available-for-sale securities		9,675	10,017
Fair Value, Recurring | Level 2 | Residential CMO
Assets measured at fair value on a recurring basis
Available-for-sale securities		4,442	3,345
Fair Value, Recurring | Level 2 | Commercial MBS
Assets measured at fair value on a recurring basis
Available-for-sale securities		1,782	1,752
Fair Value, Recurring | Level 2 | Other agencies
Assets measured at fair value on a recurring basis
Available-for-sale securities		113	130
Fair Value, Recurring | Level 2 | Municipal securities
Assets measured at fair value on a recurring basis
Available-for-sale securities		25	34
Fair Value, Recurring | Level 2 | Corporate debt
Assets measured at fair value on a recurring basis
Available-for-sale securities		175	1,055
Fair Value, Recurring | Level 2 | Asset-backed securities
Assets measured at fair value on a recurring basis
Available-for-sale securities		221	262
Fair Value, Recurring | Level 2 | Private-label CMO
Assets measured at fair value on a recurring basis
Available-for-sale securities		81	88
Fair Value, Recurring | Level 2 | Other securities/sovereign debt
Assets measured at fair value on a recurring basis
Available-for-sale securities		10	10
Fair Value, Recurring | Level 3
Assets measured at fair value on a recurring basis
Trading account securities		0	0
Available-for-sale securities		4,151	4,024
Other securities		0	0
Loans held for sale		0	0
Loans Accounted for Under FVO		63	61
MSRs		576	573
Gross amounts of recognized assets		9	4
Assets held in trust for deferred compensation plans		0	0
Short-term borrowings		0
Liabilities measured at fair value on a recurring basis
Long-term debt		0	0
Gross amounts of recognized liabilities		6	2
Fair Value, Recurring | Level 3 | U.S. Treasury
Assets measured at fair value on a recurring basis
Available-for-sale securities		0	0
Fair Value, Recurring | Level 3 | Residential MBS
Assets measured at fair value on a recurring basis
Available-for-sale securities		0	0
Fair Value, Recurring | Level 3 | Residential CMO
Assets measured at fair value on a recurring basis
Available-for-sale securities		0	0
Fair Value, Recurring | Level 3 | Commercial MBS
Assets measured at fair value on a recurring basis
Available-for-sale securities		0	0
Fair Value, Recurring | Level 3 | Other agencies
Assets measured at fair value on a recurring basis
Available-for-sale securities		0	0
Fair Value, Recurring | Level 3 | Municipal securities
Assets measured at fair value on a recurring basis
Available-for-sale securities		4,090	3,954
Fair Value, Recurring | Level 3 | Corporate debt
Assets measured at fair value on a recurring basis
Available-for-sale securities		0	0
Fair Value, Recurring | Level 3 | Asset-backed securities
Assets measured at fair value on a recurring basis
Available-for-sale securities		38	49
Fair Value, Recurring | Level 3 | Private-label CMO
Assets measured at fair value on a recurring basis
Available-for-sale securities		23	21
Fair Value, Recurring | Level 3 | Other securities/sovereign debt
Assets measured at fair value on a recurring basis
Available-for-sale securities		$ 0	$ 0

[1] Includes VIE balances in net loans and leases, other assets, long-term debt, and other liabilities of $769 million, $334 million, $694 million, and $123 million, respectively, at September 30, 2025, and $1.1 billion, $264 million, $1.0 billion, and $109 million, respectively, at December 31, 2024. See Note 15 - “Variable Interest Entities” for additional information.