LOANS - Corporate Loans (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022 USD ($) category	Sep. 30, 2021 USD ($)	Sep. 30, 2022 USD ($) category	Sep. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)
Loans and Leases Receivable Disclosure [Abstract]
Number of loan categories | category	2		2
Loans
Total loans, net of unearned income	$ 645,960		$ 645,960		$ 667,767
Lease financing
Loans
Total loans, net of unearned income	400		400		500
Corporate
Loans
Loans sold and/or reclassified to held-for-sale	2,200	$ 1,000	3,700	$ 4,100
Total loans, net of unearned income	288,377		288,377		291,233
Unearned income	(750)		(750)		(770)
Corporate | Commercial and industrial
Loans
Total loans, net of unearned income	151,610		151,610		147,004
Corporate | Financial institutions
Loans
Total loans, net of unearned income	66,904		66,904		71,767
Corporate | Mortgage and real estate
Loans
Total loans, net of unearned income	21,720		21,720		20,291
Corporate | Lease financing
Loans
Total loans, net of unearned income	431		431		455
Corporate | In North America offices
Loans
Total loans, net of unearned income	136,024		136,024		134,691
Corporate | In North America offices | Commercial and industrial
Loans
Total loans, net of unearned income	52,990		52,990		48,364
Corporate | In North America offices | Financial institutions
Loans
Total loans, net of unearned income	43,667		43,667		49,804
Corporate | In North America offices | Mortgage and real estate
Loans
Total loans, net of unearned income	17,762		17,762		15,965
Corporate | In North America offices | Installment and other
Loans
Total loans, net of unearned income	21,222		21,222		20,143
Corporate | In North America offices | Lease financing
Loans
Total loans, net of unearned income	383		383		415
Corporate | In offices outside North America
Loans
Total loans, net of unearned income	152,353		152,353		156,542
Corporate | In offices outside North America | Commercial and industrial
Loans
Total loans, net of unearned income	100,570		100,570		102,735
Corporate | In offices outside North America | Financial institutions
Loans
Total loans, net of unearned income	23,604		23,604		22,158
Corporate | In offices outside North America | Mortgage and real estate
Loans
Total loans, net of unearned income	4,005		4,005		4,374
Corporate | In offices outside North America | Installment and other
Loans
Total loans, net of unearned income	19,653		19,653		22,812
Corporate | In offices outside North America | Lease financing
Loans
Total loans, net of unearned income	48		48		40
Corporate | In offices outside North America | Government and official institutions
Loans
Total loans, net of unearned income	$ 4,473		$ 4,473		$ 4,423