SECURITIES - Schedule of Cumulative Credit Losses Recognized in Earnings (Details) - Available-for-sale Securities - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Cumulative balance at beginning of period		$ 75	$ 66	$ 62
Credit impairments recognized in earnings on securities that have been previously impaired		7	12	7
Reductions due to increases in cash flow expectations on impaired securities (1)	[1]	(2)	(3)	(3)
Cumulative balance at end of period		$ 80	$ 75	$ 66

[1] Reported in interest income from investment securities on the Consolidated Statements of Operations.