LOANS - Corporate Loan Delinquency (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Loans receivable
Loans, net of unearned income	$ 622,444		$ 622,444		$ 644,635
Loans at fair value	5,513		5,513		$ 5,901
Corporate
Loans receivable
Loans sold and/or reclassified to held-for-sale	500	$ 1,700	$ 1,600	$ 4,200
Number of days past due, non-accrual status			90 days		90 days
Number of days past due for reversal of accrued interest and charging to earnings			90 days
Loans, equal to 30- 89 days past due and accruing	332		$ 332		$ 187
Loans, greater than or equal to 90 days past due and accruing	7		7		1
Loans, total Past due and accruing	339		339		188
Loans, total non-accrual	1,558		1,558		1,183
Loans, total current	281,689		281,689		267,385
Loans, net of unearned income	289,071		289,071		274,665
Loans at fair value	5,476		5,476		5,858
Purchased distressed loans	9		$ 9		$ 51
Loans less than this number of days past due are considered current			30 days		30 days
Corporate | Commercial and industrial
Loans receivable
Loans, equal to 30- 89 days past due and accruing	75		$ 75		$ 50
Loans, greater than or equal to 90 days past due and accruing	0		0		0
Loans, total Past due and accruing	75		75		50
Loans, total non-accrual	1,042		1,042		575
Loans, total current	116,958		116,958		109,764
Loans, net of unearned income	118,075		118,075		110,389
Corporate | Financial institutions
Loans receivable
Loans, equal to 30- 89 days past due and accruing	20		20		2
Loans, greater than or equal to 90 days past due and accruing	0		0		0
Loans, total Past due and accruing	20		20		2
Loans, total non-accrual	165		165		250
Loans, total current	64,647		64,647		67,580
Loans, net of unearned income	64,832		64,832		67,832
Corporate | Mortgage and real estate
Loans receivable
Loans, equal to 30- 89 days past due and accruing	190		190		86
Loans, greater than or equal to 90 days past due and accruing	0		0		0
Loans, total Past due and accruing	190		190		86
Loans, total non-accrual	236		236		252
Loans, total current	43,121		43,121		38,135
Loans, net of unearned income	43,547		43,547		38,473
Corporate | Leases
Loans receivable
Loans, equal to 30- 89 days past due and accruing	1		1		0
Loans, greater than or equal to 90 days past due and accruing	0		0		0
Loans, total Past due and accruing	1		1		0
Loans, total non-accrual	75		75		51
Loans, total current	1,900		1,900		2,062
Loans, net of unearned income	1,976		1,976		2,113
Corporate | Other
Loans receivable
Loans, equal to 30- 89 days past due and accruing	46		46		49
Loans, greater than or equal to 90 days past due and accruing	7		7		1
Loans, total Past due and accruing	53		53		50
Loans, total non-accrual	40		40		55
Loans, total current	55,063		55,063		49,844
Loans, net of unearned income	$ 55,156		$ 55,156		$ 49,949