LOANS - Corporate Loans (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022 USD ($) category	Jun. 30, 2021 USD ($)	Jun. 30, 2022 USD ($) category	Jun. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)
Loans and Leases Receivable Disclosure [Abstract]
Number of loan categories | category	2		2
Loans
Total loans, net of unearned income	$ 657,333		$ 657,333		$ 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	1,100	$ 1,700	1,500	$ 3,100
Total loans, net of unearned income	301,728		301,728		291,233
Unearned income	(759)		(759)		(770)
Corporate | Commercial and industrial
Loans
Total loans, net of unearned income	161,338		161,338		147,004
Corporate | Financial institutions
Loans
Total loans, net of unearned income	70,448		70,448		71,767
Corporate | Mortgage and real estate
Loans
Total loans, net of unearned income	21,761		21,761		20,291
Corporate | Lease financing
Loans
Total loans, net of unearned income	432		432		455
Corporate | In North America offices
Loans
Total loans, net of unearned income	140,115		140,115		134,691
Corporate | In North America offices | Commercial and industrial
Loans
Total loans, net of unearned income	55,823		55,823		48,364
Corporate | In North America offices | Financial institutions
Loans
Total loans, net of unearned income	46,088		46,088		49,804
Corporate | In North America offices | Mortgage and real estate
Loans
Total loans, net of unearned income	17,359		17,359		15,965
Corporate | In North America offices | Installment and other
Loans
Total loans, net of unearned income	20,466		20,466		20,143
Corporate | In North America offices | Lease financing
Loans
Total loans, net of unearned income	379		379		415
Corporate | In offices outside North America
Loans
Total loans, net of unearned income	161,613		161,613		156,542
Corporate | In offices outside North America | Commercial and industrial
Loans
Total loans, net of unearned income	108,274		108,274		102,735
Corporate | In offices outside North America | Financial institutions
Loans
Total loans, net of unearned income	24,654		24,654		22,158
Corporate | In offices outside North America | Mortgage and real estate
Loans
Total loans, net of unearned income	4,455		4,455		4,374
Corporate | In offices outside North America | Installment and other
Loans
Total loans, net of unearned income	19,862		19,862		22,812
Corporate | In offices outside North America | Lease financing
Loans
Total loans, net of unearned income	53		53		40
Corporate | In offices outside North America | Government and official institutions
Loans
Total loans, net of unearned income	$ 4,315		$ 4,315		$ 4,423