SECURITIES - Schedule of Investments in Continuous Loss Positions (Details) $ in Millions	Dec. 31, 2018 USD ($) Securities	Dec. 31, 2017 USD ($) Securities
Number of Issues
Less than 12 Months | Securities	176	300
12 Months or Longer | Securities	440	162
Total | Securities	616	462
Fair Value
Less than 12 Months	$ 5,020	$ 10,218
12 Months or Longer	15,196	8,145
Total	20,216	18,363
Gross Unrealized Losses
Less than 12 Months	(90)	(98)
12 Months or Longer	(654)	(232)
Total	$ (744)	$ (330)
Federal agencies and U.S. government sponsored entities
Number of Issues
Less than 12 Months | Securities	166	294
12 Months or Longer | Securities	429	152
Total | Securities	595	446
Fair Value
Less than 12 Months	$ 4,881	$ 10,163
12 Months or Longer	15,124	8,061
Total	20,005	18,224
Gross Unrealized Losses
Less than 12 Months	(89)	(97)
12 Months or Longer	(648)	(226)
Total	$ (737)	$ (323)
Other/non-agency
Number of Issues
Less than 12 Months | Securities	10	6
12 Months or Longer | Securities	11	10
Total | Securities	21	16
Fair Value
Less than 12 Months	$ 139	$ 55
12 Months or Longer	72	84
Total	211	139
Gross Unrealized Losses
Less than 12 Months	(1)	(1)
12 Months or Longer	(6)	(6)
Total	$ (7)	$ (7)