INVESTMENT SECURITIES - Schedule of Investment Securities' Gross Unrealized Losses and Fair Value by Investment Category (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Available-for-sale debt securities:
Available-for-sale debt securities, Less than 12 months, Fair Value	$ 19,611	$ 1,530,406
Available-for-sale debt securities, Less than 12 months, Unrealized Loss	342	171,140
Available-for-sale debt securities, 12 months or longer, Fair Value	3,819,041	2,562,615
Available-for-sale debt securities, 12 months or longer, Unrealized Loss	657,631	570,350
Available-for-sale debt securities, Total, Fair Value	3,838,652	4,093,021
Available-for-sale debt securities, Total, Unrealized Loss	657,973	741,490
CMO
Available-for-sale debt securities:
Available-for-sale debt securities, Less than 12 months, Fair Value	0	158,449
Available-for-sale debt securities, Less than 12 months, Unrealized Loss	0	13,855
Available-for-sale debt securities, 12 months or longer, Fair Value	464,619	347,931
Available-for-sale debt securities, 12 months or longer, Unrealized Loss	96,333	88,599
Available-for-sale debt securities, Total, Fair Value	464,619	506,380
Available-for-sale debt securities, Total, Unrealized Loss	96,333	102,454
FNMA MBS
Available-for-sale debt securities:
Available-for-sale debt securities, Less than 12 months, Fair Value	9,068	1,237,560
Available-for-sale debt securities, Less than 12 months, Unrealized Loss	125	145,752
Available-for-sale debt securities, 12 months or longer, Fair Value	3,026,520	2,012,698
Available-for-sale debt securities, 12 months or longer, Unrealized Loss	502,449	427,026
Available-for-sale debt securities, Total, Fair Value	3,035,588	3,250,258
Available-for-sale debt securities, Total, Unrealized Loss	502,574	572,778
FHLMC MBS
Available-for-sale debt securities:
Available-for-sale debt securities, Less than 12 months, Fair Value	0	102,321
Available-for-sale debt securities, Less than 12 months, Unrealized Loss	0	9,268
Available-for-sale debt securities, 12 months or longer, Fair Value	115,525	19,671
Available-for-sale debt securities, 12 months or longer, Unrealized Loss	11,324	4,287
Available-for-sale debt securities, Total, Fair Value	115,525	121,992
Available-for-sale debt securities, Total, Unrealized Loss	11,324	13,555
GNMA MBS
Available-for-sale debt securities:
Available-for-sale debt securities, Less than 12 months, Fair Value	10,543	32,076
Available-for-sale debt securities, Less than 12 months, Unrealized Loss	217	2,265
Available-for-sale debt securities, 12 months or longer, Fair Value	31,681	4,030
Available-for-sale debt securities, 12 months or longer, Unrealized Loss	2,782	713
Available-for-sale debt securities, Total, Fair Value	42,224	36,106
Available-for-sale debt securities, Total, Unrealized Loss	2,999	2,978
GSE agency notes
Available-for-sale debt securities:
Available-for-sale debt securities, Less than 12 months, Fair Value	0	0
Available-for-sale debt securities, Less than 12 months, Unrealized Loss	0	0
Available-for-sale debt securities, 12 months or longer, Fair Value	180,696	178,285
Available-for-sale debt securities, 12 months or longer, Unrealized Loss	44,743	49,725
Available-for-sale debt securities, Total, Fair Value	180,696	178,285
Available-for-sale debt securities, Total, Unrealized Loss	$ 44,743	$ 49,725

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