LOANS - Consumer Loans (Details) $ in Millions	3 Months Ended
	Mar. 31, 2016 USD ($) category	Mar. 31, 2015 USD ($)	Dec. 31, 2015 USD ($)
Loans
Number of loan categories | category	2
Loans, net of unearned income	$ 618,824		$ 617,617
Consumer
Loans
Total loans	317,074		324,955
Net unearned income	826		830
Loans, net of unearned income	317,900		325,785
Loans sold and/or reclassified to held-for-sale	2,700	$ 14,000
In U.S. offices | Consumer
Loans
Total loans	196,317		202,968
In U.S. offices | Consumer | Mortgage and real estate
Loans
Total loans	79,128		80,281
In U.S. offices | Consumer | Installment, revolving credit and other
Loans
Total loans	3,504		3,480
In U.S. offices | Consumer | Cards
Loans
Total loans	106,892		112,800
In U.S. offices | Consumer | Commercial and industrial
Loans
Total loans	6,793		6,407
In offices outside the U.S. | Consumer
Loans
Total loans	120,757		121,987
In offices outside the U.S. | Consumer | Mortgage and real estate
Loans
Total loans	47,831		47,062
In offices outside the U.S. | Consumer | Installment, revolving credit and other
Loans
Total loans	28,778		29,480
In offices outside the U.S. | Consumer | Cards
Loans
Total loans	26,312		27,342
In offices outside the U.S. | Consumer | Commercial and industrial
Loans
Total loans	17,697		17,741
In offices outside the U.S. | Consumer | Lease financing
Loans
Total loans	$ 139		$ 362