RECLASSIFICATIONS OUT OF ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) - Reclassifications out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest income		$ 626	$ 624	$ 488
Interest expense		(452)	(363)	(443)
Net securities impairment losses recognized in earnings		(7)	(10)	(8)
Salaries and employee benefits		(1,636)	(1,678)	(1,652)
Income (loss) before income tax expense (benefit)		1,263	1,268	(3,468)
Income tax expense (benefit)		423	403	(42)
NET INCOME (LOSS)		840	865	(3,426)
Amount Reclassified from AOCI
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income tax expense (benefit)		17	71	(87)
NET INCOME (LOSS)		20	112	(147)
Reclassification adjustment for net derivative gains (losses) included in net income: | Amount Reclassified from AOCI
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest income	[1]	82	72	56
Interest expense	[1]	(59)	(99)	(235)
Other Income		0	0	(1)
Income (loss) before income tax expense (benefit)		23	(27)	(180)
Income tax expense (benefit)		9	(10)	(66)
NET INCOME (LOSS)		14	(17)	(114)
Reclassification of net securities gains (losses) to net income: | Amount Reclassified from AOCI
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Securities gains, net		29	28	144
Net securities impairment losses recognized in earnings		(7)	(10)	(8)
Income (loss) before income tax expense (benefit)		22	18	136
Income tax expense (benefit)		8	7	50
NET INCOME (LOSS)		14	11	86
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		(8)	192	(190)
Income (loss) before income tax expense (benefit)		(8)	192	(190)
Income tax expense (benefit)		0	74	(71)
NET INCOME (LOSS)		$ (8)	$ 118	$ (119)

[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.