FAIR VALUE MEASUREMENTS - Schedule of Financial Instruments not Recorded at Fair Value (Details) - USD ($) $ in Millions		Jun. 30, 2025	Dec. 31, 2024
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities held to maturity, carrying value	[1]	$ 8,293	$ 8,599
Debt securities held to maturity, fair value		7,379	7,540
Other loans held for sale, carrying value		1,158	33
Other loans held for sale, fair value		1,158	33
Loans pledged as collateral for FHLB borrowed funds	[2]	137,296	137,142
Loans and leases, fair value		136,748	136,293
Other assets, carrying value		772	710
Other assets, fair value		772	710
Deposits, carrying value		175,086	174,776
Deposits, fair value		175,006	174,651
Long-term borrowed funds, carrying value	[2]	12,526	12,401
Long-term borrowed funds, fair value		12,575	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		7,919	8,187
Debt securities held to maturity, fair value		7,008	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		697	979
Loans and leases, fair value		697	979
Other assets, carrying value		751	689
Other assets, fair value		751	689
Deposits, carrying value		175,086	174,776
Deposits, fair value		175,006	174,651
Long-term borrowed funds, carrying value		12,526	12,401
Long-term borrowed funds, fair value		12,575	12,247
Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities held to maturity, carrying value		374	412
Debt securities held to maturity, fair value		371	404
Other loans held for sale, carrying value		1,158	33
Other loans held for sale, fair value		1,158	33
Loans pledged as collateral for FHLB borrowed funds		136,599	136,163
Loans and leases, fair value		136,051	135,314
Other assets, carrying value		21	21
Other assets, fair value		21	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.