SECURITIES - Unrealized Loss Position (Details) $ in Thousands	Mar. 31, 2023 USD ($) security	Dec. 31, 2022 USD ($) security
Unrealized Loss Position For:
Estimated Fair Value	$ 69,238,185	$ 65,789,907
Gross Unrealized Losses	(3,462,620)	(4,963,091)
Agency Mortgage-Backed Securities
Unrealized Loss Position For:
Estimated Fair Value	30,658,507	34,321,645
Gross Unrealized Losses	$ (2,557,998)	$ (3,714,806)
Number of Securities | security	2,480	2,610
Agency Mortgage-Backed Securities | Less than 12 months
Unrealized Loss Position For:
Estimated Fair Value	$ 12,762,176	$ 33,061,267
Gross Unrealized Losses	$ (662,612)	$ (3,448,120)
Number of Securities | security	1,057	2,481
Agency Mortgage-Backed Securities | 12 Months or more
Unrealized Loss Position For:
Estimated Fair Value	$ 17,896,331	$ 1,260,378
Gross Unrealized Losses	$ (1,895,386)	$ (266,686)
Number of Securities | security	1,423	129