RECLASSIFICATIONS OUT OF ACCUMULATED OTHER COMPREHENSIVE INCOME - Reclassifications out of Accumulated Other Comprehensive Income (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest income	$ 624		$ 488		$ 624
Interest expense	(363)		(443)		(619)
Securities impairment	(10)		(8)		(24)
Salaries and employee benefits	1,678		1,652		1,743
Income (loss) before income tax expense (benefit)	1,268		(3,468)		1,024
Income tax expense (benefit)	403		(42)		381
NET INCOME (LOSS)	865		(3,426)		643
Amount Reclassified from AOCI
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income tax expense (benefit)	71		(87)		82
NET INCOME (LOSS)	112		(147)		(142)
Reclassification adjustment for net derivative gains (losses) included in net income (loss): | Amount Reclassified from AOCI
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest income	72	[1]	56	[1]	0	[1]
Interest expense	(99)	[1]	(235)	[1]	(335)	[1]
Other income	0		(1)		0
Income (loss) before income tax expense (benefit)	(27)		(180)		(335)
Income tax expense (benefit)	(10)		(66)		(123)
NET INCOME (LOSS)	(17)		(114)		(212)
Reclassification of net securities gains (losses) to net income (loss): | Amount Reclassified from AOCI
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Securities gains, net	28		144		95
Securities impairment	(10)		(8)		(24)
Income (loss) before income tax expense (benefit)	18		136		71
Income tax expense (benefit)	7		50		26
NET INCOME (LOSS)	11		86		45
Reclassification of changes related to defined benefit pension plans: | Amount Reclassified from AOCI
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Salaries and employee benefits	192		(190)		40
Income (loss) before income tax expense (benefit)	192		(190)		40
Income tax expense (benefit)	74		(71)		15
NET INCOME (LOSS)	$ 118		$ (119)		$ 25

[1] This amount includes both (a) the amortization of effective gains and losses associated with the Company's terminated cash flow hedges and (b) the current reporting period's interest settlements realized on the Company's active cash flow hedges. Both (a) and (b) were previously included on the accumulated other comprehensive loss line item on the Consolidated Balance Sheets and were subsequently recorded as adjustments to the interest expense of the underlying hedged item.