LOANS - Corporate Loans (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Loans
Loans, net of unearned income	$ 621,054	$ 644,635
Corporate
Loans
Total loans	279,888	275,219
Net unearned income (loss)	(540)	(554)
Loans, net of unearned income	279,348	274,665
Corporate | Commercial and industrial
Loans
Loans, net of unearned income	114,232	110,389
Corporate | Financial institutions
Loans
Loans, net of unearned income	66,684	67,832
Corporate | Mortgage and real estate
Loans
Loans, net of unearned income	39,359	38,473
Corporate | Lease financing
Loans
Loans, net of unearned income	2,077	2,113
In U.S. offices | Corporate
Loans
Total loans	137,758	134,829
In U.S. offices | Corporate | Commercial and industrial
Loans
Total loans	37,537	35,055
In U.S. offices | Corporate | Financial institutions
Loans
Total loans	36,054	36,272
In U.S. offices | Corporate | Mortgage and real estate
Loans
Total loans	33,145	32,537
In U.S. offices | Corporate | Installment, revolving credit and other
Loans
Total loans	29,267	29,207
In U.S. offices | Corporate | Lease financing
Loans
Total loans	1,755	1,758
In offices outside the U.S. | Corporate
Loans
Total loans	142,130	140,390
In offices outside the U.S. | Corporate | Commercial and industrial
Loans
Total loans	81,426	79,239
In offices outside the U.S. | Corporate | Financial institutions
Loans
Total loans	32,210	33,269
In offices outside the U.S. | Corporate | Mortgage and real estate
Loans
Total loans	6,311	6,031
In offices outside the U.S. | Corporate | Installment, revolving credit and other
Loans
Total loans	19,687	19,259
In offices outside the U.S. | Corporate | Lease financing
Loans
Total loans	322	356
In offices outside the U.S. | Corporate | Government and official institutions
Loans
Total loans	$ 2,174	$ 2,236