SECURITIES - Schedule of Investments in Continuous Loss Positions (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Fair Value
Less than 12 Months	$ 805
12 Months or Longer	0
Total	805
Gross Unrealized Losses
Less than 12 Months	(7)
12 Months or Longer	0
Total	(7)
Federal agencies and U.S. government sponsored entities
Fair Value
Less than 12 Months	456	$ 5,135
12 Months or Longer	0	3,748
Total	456	8,883
Gross Unrealized Losses
Less than 12 Months	(3)	(24)
12 Months or Longer	0	(52)
Total	(3)	$ (76)
Other/non-agency
Fair Value
Less than 12 Months	349
12 Months or Longer	0
Total	349
Gross Unrealized Losses
Less than 12 Months	(4)
12 Months or Longer	0
Total	$ (4)