SECURITIES - Schedule of Investments in Continuous Loss Positions (Details) $ in Millions	Dec. 31, 2019 USD ($) security	Dec. 31, 2018 USD ($) security
Number of Issues
Less than 12 Months | security	106	176
12 Months or Longer | security	120	440
Total | security	226	616
Fair Value
Less than 12 Months	$ 5,135	$ 5,020
12 Months or Longer	3,748	15,196
Total	8,883	20,216
Gross Unrealized Losses
Less than 12 Months	(24)	(90)
12 Months or Longer	(52)	(654)
Total	$ (76)	$ (744)
Federal agencies and U.S. government sponsored entities
Number of Issues
Less than 12 Months | security	106	166
12 Months or Longer | security	120	429
Total | security	226	595
Fair Value
Less than 12 Months	$ 5,135	$ 4,881
12 Months or Longer	3,748	15,124
Total	8,883	20,005
Gross Unrealized Losses
Less than 12 Months	(24)	(89)
12 Months or Longer	(52)	(648)
Total	$ (76)	$ (737)
Other/non-agency
Number of Issues
Less than 12 Months | security	0	10
12 Months or Longer | security	0	11
Total | security	0	21
Fair Value
Less than 12 Months	$ 0	$ 139
12 Months or Longer	0	72
Total	0	211
Gross Unrealized Losses
Less than 12 Months	0	(1)
12 Months or Longer	0	(6)
Total	$ 0	$ (7)