SECURITIES - Schedule of Investments in Continuous Loss Positions (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Fair Value
Less than 12 Months	$ 3,044	$ 17,574
12 Months or Longer	20,505	5,634
Total	23,549	23,208
Gross Unrealized Losses
Less than 12 Months	(24)	(1,363)
12 Months or Longer	(1,999)	(1,099)
Total	(2,023)	(2,462)
U.S. Treasury and other
Fair Value
Less than 12 Months	49	3,356
12 Months or Longer	3,245	0
Total	3,294	3,356
Gross Unrealized Losses
Less than 12 Months	0	(193)
12 Months or Longer	(139)	0
Total	(139)	(193)
Total mortgage-backed securities
Fair Value
Less than 12 Months	2,939	13,433
12 Months or Longer	16,653	5,213
Total	19,592	18,646
Gross Unrealized Losses
Less than 12 Months	(24)	(1,144)
12 Months or Longer	(1,857)	(1,083)
Total	(1,881)	(2,227)
Federal agencies and U.S. government sponsored entities
Fair Value
Less than 12 Months	2,939	13,353
12 Months or Longer	16,398	5,042
Total	19,337	18,395
Gross Unrealized Losses
Less than 12 Months	(24)	(1,136)
12 Months or Longer	(1,833)	(1,062)
Total	(1,857)	(2,198)
Other/non-agency
Fair Value
Less than 12 Months	0	80
12 Months or Longer	255	171
Total	255	251
Gross Unrealized Losses
Less than 12 Months	0	(8)
12 Months or Longer	(24)	(21)
Total	(24)	(29)
Collateralized loan obligations
Fair Value
Less than 12 Months	56	785
12 Months or Longer	607	421
Total	663	1,206
Gross Unrealized Losses
Less than 12 Months	0	(26)
12 Months or Longer	(3)	(16)
Total	$ (3)	$ (42)