SECURITIES - Schedule of Cumulative Credit Losses Recognized in Earnings (Details) - Available-for-sale Securities - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Cumulative balance at beginning of period	$ 62	$ 56	$ 55
Credit impairments recognized in earnings on securities that have been previously impaired	7	10	8
Reductions due to increases in cash flow expectations on impaired securities	(3)	(4)	(7)
Cumulative balance at end of period	$ 66	$ 62	$ 56