FAIR VALUE MEASUREMENTS - Schedule of Financial Instruments not Recorded at Fair Value (Details) - USD ($) $ in Millions		Mar. 31, 2025	Dec. 31, 2024
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities held to maturity, carrying value	[1]	$ 8,469	$ 8,599
Debt securities held to maturity, fair value		7,515	7,540
Other loans held for sale, carrying value		1,683	33
Other loans held for sale, fair value		1,683	33
Loans pledged as collateral for FHLB borrowed funds	[2]	135,621	137,142
Loans and leases, fair value		134,844	136,293
Other assets, carrying value		711	710
Other assets, fair value		711	710
Deposits, carrying value		177,576	174,776
Deposits, fair value		177,508	174,651
Long-term borrowed funds, carrying value	[2]	12,267	12,401
Long-term borrowed funds, fair value		12,222	12,247
Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities held to maturity, carrying value		0	0
Debt securities held to maturity, fair value		0	0
Other loans held for sale, carrying value		0	0
Other loans held for sale, fair value		0	0
Loans pledged as collateral for FHLB borrowed funds		0	0
Loans and leases, fair value		0	0
Other assets, carrying value		0	0
Other assets, fair value		0	0
Deposits, carrying value		0	0
Deposits, fair value		0	0
Long-term borrowed funds, carrying value		0	0
Long-term borrowed funds, fair value		0	0
Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities held to maturity, carrying value		8,077	8,187
Debt securities held to maturity, fair value		7,129	7,136
Other loans held for sale, carrying value		0	0
Other loans held for sale, fair value		0	0
Loans pledged as collateral for FHLB borrowed funds		910	979
Loans and leases, fair value		910	979
Other assets, carrying value		689	689
Other assets, fair value		689	689
Deposits, carrying value		177,576	174,776
Deposits, fair value		177,508	174,651
Long-term borrowed funds, carrying value		12,267	12,401
Long-term borrowed funds, fair value		12,222	12,247
Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities held to maturity, carrying value		392	412
Debt securities held to maturity, fair value		386	404
Other loans held for sale, carrying value		1,683	33
Other loans held for sale, fair value		1,683	33
Loans pledged as collateral for FHLB borrowed funds		134,711	136,163
Loans and leases, fair value		133,934	135,314
Other assets, carrying value		22	21
Other assets, fair value		22	21
Deposits, carrying value		0	0
Deposits, fair value		0	0
Long-term borrowed funds, carrying value		0	0
Long-term borrowed funds, fair value		$ 0	$ 0

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

[2] Includes amounts in consolidated VIEs. See Note 6 for additional information.