LOANS - Consumer Loans (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015 USD ($) category	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) category	Sep. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)
Loans
Number of loan categories | category	2		2
Loans, net of unearned income	$ 622,444		$ 622,444		$ 644,635
Consumer
Loans
Total loans	334,064		334,064		370,652
Net unearned income	(691)		(691)		(682)
Loans, net of unearned income	333,373		333,373		369,970
Loans sold and/or reclassified to held-for-sale	1,500	$ 1,800	16,000	$ 5,600
Consumer | In U.S. offices
Loans
Total loans	207,835		207,835		229,860
Consumer | In U.S. offices | Mortgage and real estate
Loans
Total loans	89,155		89,155		96,533
Consumer | In U.S. offices | Installment, revolving credit and other
Loans
Total loans	4,999		4,999		14,450
Consumer | In U.S. offices | Cards
Loans
Total loans	107,244		107,244		112,982
Consumer | In U.S. offices | Commercial and industrial
Loans
Total loans	6,437		6,437		5,895
Consumer | In offices outside the U.S.
Loans
Total loans	126,229		126,229		140,792
Consumer | In offices outside the U.S. | Mortgage and real estate
Loans
Total loans	47,295		47,295		54,462
Consumer | In offices outside the U.S. | Installment, revolving credit and other
Loans
Total loans	29,702		29,702		31,128
Consumer | In offices outside the U.S. | Cards
Loans
Total loans	26,865		26,865		32,032
Consumer | In offices outside the U.S. | Commercial and industrial
Loans
Total loans	21,929		21,929		22,561
Consumer | In offices outside the U.S. | Lease financing
Loans
Total loans	$ 438		$ 438		$ 609