LOANS - Corporate Loans (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Loans
Loans, net of unearned income	$ 622,444	$ 644,635
Corporate
Loans
Total loans	289,681	275,219
Net unearned income (loss)	(610)	(554)
Loans, net of unearned income	289,071	274,665
Corporate | Commercial and industrial
Loans
Loans, net of unearned income	118,075	110,389
Corporate | Financial institutions
Loans
Loans, net of unearned income	64,832	67,832
Corporate | Mortgage and real estate
Loans
Loans, net of unearned income	43,547	38,473
Corporate | Lease financing
Loans
Loans, net of unearned income	1,976	2,113
In U.S. offices | Corporate
Loans
Total loans	149,335	134,829
In U.S. offices | Corporate | Commercial and industrial
Loans
Total loans	40,435	35,055
In U.S. offices | Corporate | Financial institutions
Loans
Total loans	38,034	36,272
In U.S. offices | Corporate | Mortgage and real estate
Loans
Total loans	37,019	32,537
In U.S. offices | Corporate | Installment, revolving credit and other
Loans
Total loans	32,129	29,207
In U.S. offices | Corporate | Lease financing
Loans
Total loans	1,718	1,758
In offices outside the U.S. | Corporate
Loans
Total loans	140,346	140,390
In offices outside the U.S. | Corporate | Commercial and industrial
Loans
Total loans	81,540	79,239
In offices outside the U.S. | Corporate | Financial institutions
Loans
Total loans	28,090	33,269
In offices outside the U.S. | Corporate | Mortgage and real estate
Loans
Total loans	6,602	6,031
In offices outside the U.S. | Corporate | Installment, revolving credit and other
Loans
Total loans	19,352	19,259
In offices outside the U.S. | Corporate | Lease financing
Loans
Total loans	259	356
In offices outside the U.S. | Corporate | Government and official institutions
Loans
Total loans	$ 4,503	$ 2,236