SECURITIES - Schedule of Investments in Continuous Loss Positions (Details) $ in Millions	Sep. 30, 2019 USD ($) Securities	Dec. 31, 2018 USD ($) Securities
Number of Issues
Less than 12 Months | Securities	156	176
12 Months or Longer | Securities	180	440
Total | Securities	336	616
Fair Value
Less than 12 Months	$ 3,180	$ 5,020
12 Months or Longer	4,939	15,196
Total	8,119	20,216
Gross Unrealized Losses
Less than 12 Months	(16)	(90)
12 Months or Longer	(73)	(654)
Total	$ (89)	$ (744)
Federal agencies and U.S. government sponsored entities
Number of Issues
Less than 12 Months | Securities	156	166
12 Months or Longer | Securities	175	429
Total | Securities	331	595
Fair Value
Less than 12 Months	$ 3,180	$ 4,881
12 Months or Longer	4,907	15,124
Total	8,087	20,005
Gross Unrealized Losses
Less than 12 Months	(16)	(89)
12 Months or Longer	(69)	(648)
Total	$ (85)	$ (737)
Other/non-agency
Number of Issues
Less than 12 Months | Securities	0	10
12 Months or Longer | Securities	5	11
Total | Securities	5	21
Fair Value
Less than 12 Months	$ 0	$ 139
12 Months or Longer	32	72
Total	32	211
Gross Unrealized Losses
Less than 12 Months	0	(1)
12 Months or Longer	(4)	(6)
Total	$ (4)	$ (7)