FAIR VALUE MEASUREMENTS - Schedule of Financial Instruments not Recorded at Fair Value (Details) - USD ($) $ in Millions		Dec. 31, 2023	Dec. 31, 2022
Financial assets:
Asset-backed investments included in HTM securities	[1]	$ 9,184	$ 9,834
Debt securities held-to-maturity, fair value	[1]	8,350	9,042
Other loans held for sale, carrying value		103	208
Other loans held for sale, fair value		103	208
Net loans and leases	[2]	143,861	154,679
Loans and leases, fair value		140,504	151,601
Other investment securities, at cost, carrying value		869	1,058
Other investment securities, at cost, estimated fair value		869	1,058
Financial liabilities:
Deposits, carrying value		177,342	180,724
Deposits, fair value		177,096	180,566
Short-term borrowed funds		505	3
Short-term borrowed funds, fair value		505	3
Long-term borrowed funds, carrying value	[2]	13,467	15,887
Long-term borrowed funds, fair value		13,012	15,469
Level 1
Financial assets:
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
Net loans and leases		0	0
Loans and leases, fair value		0	0
Other investment securities, at cost, carrying value		0	0
Other investment securities, at cost, estimated fair value		0	0
Financial liabilities:
Deposits, carrying value		0	0
Deposits, fair value		0	0
Short-term borrowed funds		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
Financial assets:
Asset-backed investments included in HTM securities		8,696	9,253
Debt securities held-to-maturity, fair value		7,887	8,506
Other loans held for sale, carrying value		0	0
Other loans held for sale, fair value		0	0
Net loans and leases		789	582
Loans and leases, fair value		789	582
Other investment securities, at cost, carrying value		851	1,038
Other investment securities, at cost, estimated fair value		851	1,038
Financial liabilities:
Deposits, carrying value		177,342	180,724
Deposits, fair value		177,096	180,566
Short-term borrowed funds		505	3
Short-term borrowed funds, fair value		505	3
Long-term borrowed funds, carrying value		13,467	15,887
Long-term borrowed funds, fair value		13,012	15,469
Level 3
Financial assets:
Asset-backed investments included in HTM securities		488	581
Debt securities held-to-maturity, fair value		463	536
Other loans held for sale, carrying value		103	208
Other loans held for sale, fair value		103	208
Net loans and leases		143,072	154,097
Loans and leases, fair value		139,715	151,019
Other investment securities, at cost, carrying value		18	20
Other investment securities, at cost, estimated fair value		18	20
Financial liabilities:
Deposits, carrying value		0	0
Deposits, fair value		0	0
Short-term borrowed funds		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 11 for additional information.