SECURITIES - Income Recognized from Investment Securities (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Interest Income, Securities, Operating, by Taxable Status [Abstract]
Taxable	$ 154	$ 155	$ 468	$ 458
Non-taxable	0	0	0	0
Total interest income from investment securities	154	155	468	458
Gain (Loss) on Sale of Investments [Abstract]
Gains on sale of debt securities	7	7	29	32
Losses on sale of debt securities	(7)	(5)	(12)	(5)
Debt securities gains, net	0	2	17	27
Equity securities gains	$ 0	$ 0	$ 3	$ 0