LOANS - Corporate Loan Delinquency (Details) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Loans receivable
Loans, net of unearned income	$ 621,054,000,000		$ 644,635,000,000
Loans at fair value	6,575,000,000		5,901,000,000
Corporate
Loans receivable
Loans sold and/or reclassified to held-for-sale	600,000,000	1,100,000,000
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	857,000,000		187,000,000
Loans, greater than or equal to 90 days past due and accruing	6,000,000		1,000,000
Loans, total Past due and accruing	863,000,000		188,000,000
Loans, total non-accrual	1,161,000,000		1,183,000,000
Loans, total current	270,742,000,000		267,385,000,000
Loans, net of unearned income	279,348,000,000		274,665,000,000
Loans at fair value	6,537,000,000		5,858,000,000
Purchased distressed loans	45,000,000		51,000,000
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	541,000,000		50,000,000
Loans, greater than or equal to 90 days past due and accruing	1,000,000		0
Loans, total Past due and accruing	542,000,000		50,000,000
Loans, total non-accrual	592,000,000		575,000,000
Loans, total current	113,098,000,000		109,764,000,000
Loans, net of unearned income	114,232,000,000		110,389,000,000
Corporate | Financial institutions
Loans receivable
Loans, equal to 30- 89 days past due and accruing	95,000,000		2,000,000
Loans, greater than or equal to 90 days past due and accruing	0		0
Loans, total Past due and accruing	95,000,000		2,000,000
Loans, total non-accrual	239,000,000		250,000,000
Loans, total current	66,350,000,000		67,580,000,000
Loans, net of unearned income	66,684,000,000		67,832,000,000
Corporate | Mortgage and real estate
Loans receivable
Loans, equal to 30- 89 days past due and accruing	132,000,000		86,000,000
Loans, greater than or equal to 90 days past due and accruing	0		0
Loans, total Past due and accruing	132,000,000		86,000,000
Loans, total non-accrual	246,000,000		252,000,000
Loans, total current	38,981,000,000		38,135,000,000
Loans, net of unearned income	39,359,000,000		38,473,000,000
Corporate | Leases
Loans receivable
Loans, equal to 30- 89 days past due and accruing	0		0
Loans, greater than or equal to 90 days past due and accruing	1,000,000		0
Loans, total Past due and accruing	1,000,000		0
Loans, total non-accrual	49,000,000		51,000,000
Loans, total current	2,027,000,000		2,062,000,000
Loans, net of unearned income	2,077,000,000		2,113,000,000
Corporate | Other
Loans receivable
Loans, equal to 30- 89 days past due and accruing	89,000,000		49,000,000
Loans, greater than or equal to 90 days past due and accruing	4,000,000		1,000,000
Loans, total Past due and accruing	93,000,000		50,000,000
Loans, total non-accrual	35,000,000		55,000,000
Loans, total current	50,286,000,000		49,844,000,000
Loans, net of unearned income	$ 50,414,000,000		$ 49,949,000,000