FAIR VALUE MEASUREMENTS - Schedule of Financial Instruments not Recorded at Fair Value (Details) - USD ($) $ in Millions		Jun. 30, 2024	Dec. 31, 2023
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset-backed investments included in HTM securities	[1]	$ 8,895	$ 9,184
Fair Value		7,924	8,350
Other loans held for sale, carrying value		92	103
Other loans held for sale, fair value		92	103
Loans pledged as collateral for FHLB borrowed funds	[2]	139,717	143,861
Loans and leases, fair value		137,363	140,504
Other assets, carrying value		731	869
Other assets, fair value		731	869
Deposits, carrying value		176,352	177,342
Deposits, fair value		176,102	177,096
Short-term borrowed funds, carrying value		2	505
Short-term borrowed funds, fair value		2	505
Long-term borrowed funds, carrying value	[2]	13,082	13,467
Long-term borrowed funds, fair value		12,719	13,012
Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset-backed investments included in HTM securities		0	0
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
Short-term borrowed funds, carrying value		0	0
Short-term borrowed funds, 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]
Asset-backed investments included in HTM securities		8,447	8,696
Fair Value		7,490	7,887
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		934	789
Loans and leases, fair value		934	789
Other assets, carrying value		709	851
Other assets, fair value		709	851
Deposits, carrying value		176,352	177,342
Deposits, fair value		176,102	177,096
Short-term borrowed funds, carrying value		2	505
Short-term borrowed funds, fair value		2	505
Long-term borrowed funds, carrying value		13,082	13,467
Long-term borrowed funds, fair value		12,719	13,012
Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset-backed investments included in HTM securities		448	488
Fair Value		434	463
Other loans held for sale, carrying value		92	103
Other loans held for sale, fair value		92	103
Loans pledged as collateral for FHLB borrowed funds		138,783	143,072
Loans and leases, fair value		136,429	139,715
Other assets, carrying value		22	18
Other assets, fair value		22	18
Deposits, carrying value		0	0
Deposits, fair value		0	0
Short-term borrowed funds, carrying value		0	0
Short-term borrowed funds, 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.