DERIVATIVES - Effect of Derivative Instruments on Net Income (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivative Instruments, Gain (Loss) [Line Items]
Amounts reclassified from OCI to interest expense		$ (747)	$ (508)	$ (452)
Amount Reclassified from AOCI
Derivative Instruments, Gain (Loss) [Line Items]
Effective portion of (loss) gain recognized in OCI	[1]	(23)	(100)	150
Amount Reclassified from AOCI | Net Unrealized (Losses) Gains on Derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Amounts reclassified from OCI to interest income	[2]	25	90	82
Amounts reclassified from OCI to interest expense	[2]	0	(27)	(59)
Amounts reclassified from OCI to other income	[3]	$ 0	$ (5)	$ 0

[1] The cumulative effective gains and losses on the Company’s cash flow hedging activities are included on the accumulated other comprehensive loss line item on the Consolidated Balance Sheets.

[2] 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 income or expense of the underlying hedged item.

[3] This includes gains and losses attributable to previously hedged cash flows where the likelihood occurrence of those cash flows is no longer probable.