FAIR VALUE MEASUREMENTS - Schedule of Financial Instruments not Recorded at Fair Value (Details) - USD ($) $ in Millions		Sep. 30, 2024	Dec. 31, 2023
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset-backed investments included in HTM securities	[1]	$ 8,738	$ 9,184
Fair Value		8,067	8,350
Other loans held for sale, carrying value		49	103
Other loans held for sale, fair value		49	103
Loans pledged as collateral for FHLB borrowed funds	[2]	139,553	143,861
Loans and leases, fair value		139,662	140,504
Other assets, carrying value		732	869
Other assets, fair value		732	869
Deposits, carrying value		175,188	177,342
Deposits, fair value		175,061	177,096
Short-term borrowed funds, carrying value		15	505
Short-term borrowed funds, fair value			505
Long-term borrowed funds, carrying value	[2]	13,944	13,467
Long-term borrowed funds, fair value		13,977	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
Short-term borrowed funds, fair value			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		8,308	8,696
Fair Value		7,645	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		1,136	789
Loans and leases, fair value		1,136	789
Other assets, carrying value		710	851
Other assets, fair value		710	851
Deposits, carrying value		175,188	177,342
Deposits, fair value		175,061	177,096
Short-term borrowed funds, carrying value			505
Short-term borrowed funds, fair value			505
Long-term borrowed funds, carrying value		13,944	13,467
Long-term borrowed funds, fair value		13,977	13,012
Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset-backed investments included in HTM securities		430	488
Fair Value		422	463
Other loans held for sale, carrying value		49	103
Other loans held for sale, fair value		49	103
Loans pledged as collateral for FHLB borrowed funds		138,417	143,072
Loans and leases, fair value		138,526	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
Short-term borrowed funds, fair value			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.