FAIR VALUE MEASUREMENTS - Schedule of Financial Instruments not Recorded at Fair Value (Details) - USD ($) $ in Millions		Jun. 30, 2022	Dec. 31, 2021
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset-backed investments included in HTM securities	[1]	$ 9,567	$ 2,242
Debt Securities held-to-maturity, fair value		9,361	2,289
Other loans held for sale, carrying value		2,078	735
Other loans held for sale, fair value		2,058	735
Loans and leases, carrying value		156,172	128,163
Loans and leases, fair value		152,496	128,156
Other assets, carrying value		1,162	624
Other assets, fair value		1,162	624
Deposits, carrying value		178,925	154,361
Deposits, fair value		178,807	154,366
Short-term borrowed funds, carrying value		3,763	74
Short-term borrowed funds, fair value		3,763	74
Long-term borrowed funds, carrying value		14,440	6,932
Long-term borrowed funds, fair value		14,299	7,188
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		8,921	1,505
Debt Securities held-to-maturity, fair value		8,747	1,557
Other loans held for sale, carrying value		0	0
Other loans held for sale, fair value		0	0
Loans and leases, carrying value		579	645
Loans and leases, fair value		579	645
Other assets, carrying value		1,146	609
Other assets, fair value		1,146	609
Deposits, carrying value		178,925	154,361
Deposits, fair value		178,807	154,366
Short-term borrowed funds, carrying value		3,763	74
Short-term borrowed funds, fair value		3,763	74
Long-term borrowed funds, carrying value		14,440	6,932
Long-term borrowed funds, fair value		14,299	7,188
Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Asset-backed investments included in HTM securities		646	737
Debt Securities held-to-maturity, fair value		614	732
Other loans held for sale, carrying value		2,078	735
Other loans held for sale, fair value		2,058	735
Loans and leases, carrying value		155,593	127,518
Loans and leases, fair value		151,917	127,511
Other assets, carrying value		16	15
Other assets, fair value		16	15
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.