FAIR VALUE MEASUREMENTS - Schedule of Financial Instruments not Recorded at Fair Value (Details) - USD ($) $ in Millions		Mar. 31, 2023	Dec. 31, 2022
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset-backed investments included in HTM securities	[1]	$ 9,677	$ 9,834
Debt Securities held-to-maturity, fair value		9,064	9,042
Other loans held for sale, carrying value		1,000	208
Other loans held for sale, fair value		1,000	208
Loans and leases, carrying value		154,688	156,662
Loans and leases, fair value		149,332	151,601
Other assets, carrying value		1,228	1,058
Other assets, fair value		1,228	1,058
Deposits, carrying value		172,194	180,724
Deposits, fair value		172,096	180,566
Short-term borrowed funds, carrying value		1,018	3
Short-term borrowed funds, fair value		1,018	3
Long-term borrowed funds, carrying value		18,855	15,887
Long-term borrowed funds, fair value		18,155	15,469
Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset-backed investments included in HTM securities		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 and leases, carrying value		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		9,125	9,253
Debt Securities held-to-maturity, fair value		8,540	8,506
Other loans held for sale, carrying value		0	0
Other loans held for sale, fair value		0	0
Loans and leases, carrying value		671	582
Loans and leases, fair value		671	582
Other assets, carrying value		1,208	1,038
Other assets, fair value		1,208	1,038
Deposits, carrying value		172,194	180,724
Deposits, fair value		172,096	180,566
Short-term borrowed funds, carrying value		1,018	3
Short-term borrowed funds, fair value		1,018	3
Long-term borrowed funds, carrying value		18,855	15,887
Long-term borrowed funds, fair value		18,155	15,469
Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset-backed investments included in HTM securities		552	581
Debt Securities held-to-maturity, fair value		524	536
Other loans held for sale, carrying value		1,000	208
Other loans held for sale, fair value		1,000	208
Loans and leases, carrying value		154,017	156,080
Loans and leases, fair value		148,661	151,019
Other assets, carrying value		20	20
Other assets, fair value		20	20
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.