RECLASSIFICATIONS OUT OF ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) - Reclassifications out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest expense		$ (155)	$ (115)
Net securities impairment losses recognized in earnings		(1)	(1)
Salaries and employee benefits		(444)	(425)
Income before income tax expense		434	332
Income tax expense		114	109
NET INCOME		320	223
Amount Reclassified from AOCI
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income tax expense		3	7
NET INCOME		5	11
Reclassification adjustment for net derivative gains included in net income: | Amount Reclassified from AOCI
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest income	[1]	12	22
Interest expense	[1]	(2)	(8)
Income before income tax expense		10	14
Income tax expense		4	6
NET INCOME		6	8
Reclassification of net securities gains to net income: | Amount Reclassified from AOCI
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Securities gains, net		4	9
Net securities impairment losses recognized in earnings		(1)	(1)
Income before income tax expense		3	8
Income tax expense		1	3
NET INCOME		2	5
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		(5)	(4)
Income before income tax expense		(5)	(4)
Income tax expense		(2)	(2)
NET INCOME		$ (3)	$ (2)

[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.