SECURITIES - Schedule of Investments in Continuous Loss Positions (Details) $ in Millions	Jun. 30, 2019 USD ($) Securities	Dec. 31, 2018 USD ($) Securities
Number of Issues
Less than 12 Months | Securities	19	176
12 Months or Longer | Securities	356	440
Total | Securities	375	616
Fair Value
Less than 12 Months	$ 882	$ 5,020
12 Months or Longer	11,348	15,196
Total	12,230	20,216
Gross Unrealized Losses
Less than 12 Months	(1)	(90)
12 Months or Longer	(170)	(654)
Total	$ (171)	$ (744)
Federal agencies and U.S. government sponsored entities
Number of Issues
Less than 12 Months | Securities	19	166
12 Months or Longer | Securities	349	429
Total | Securities	368	595
Fair Value
Less than 12 Months	$ 882	$ 4,881
12 Months or Longer	11,307	15,124
Total	12,189	20,005
Gross Unrealized Losses
Less than 12 Months	(1)	(89)
12 Months or Longer	(166)	(648)
Total	$ (167)	$ (737)
Other/non-agency
Number of Issues
Less than 12 Months | Securities	0	10
12 Months or Longer | Securities	7	11
Total | Securities	7	21
Fair Value
Less than 12 Months	$ 0	$ 139
12 Months or Longer	41	72
Total	41	211
Gross Unrealized Losses
Less than 12 Months	0	(1)
12 Months or Longer	(4)	(6)
Total	$ (4)	$ (7)