INVESTMENT SECURITIES - Schedule of Investment Securities' Gross Unrealized Losses and Fair Value by Investment Category (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Available-for-sale debt securities:
Available-for-sale debt securities, Less than 12 months, Fair value	$ 26,529	$ 19,611
Available-for-sale debt securities, Less than 12 months, Unrealized loss	502	342
Available-for-sale debt securities, 12 months or longer, Fair value	3,694,657	3,819,041
Available-for-sale debt securities, 12 months or longer, Unrealized loss	710,064	657,631
Available-for-sale debt securities, Total, Fair value	3,721,186	3,838,652
Available-for-sale debt securities, Total, Unrealized loss	710,566	657,973
CMO
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	451,891	464,619
Available-for-sale debt securities, 12 months or longer, Unrealized loss	99,992	96,333
Available-for-sale debt securities, Total, Fair value	451,891	464,619
Available-for-sale debt securities, Total, Unrealized loss	99,992	96,333
FNMA MBS
Available-for-sale debt securities:
Available-for-sale debt securities, Less than 12 months, Fair value	18,744	9,068
Available-for-sale debt securities, Less than 12 months, Unrealized loss	275	125
Available-for-sale debt securities, 12 months or longer, Fair value	2,916,614	3,026,520
Available-for-sale debt securities, 12 months or longer, Unrealized loss	548,020	502,449
Available-for-sale debt securities, Total, Fair value	2,935,358	3,035,588
Available-for-sale debt securities, Total, Unrealized loss	548,295	502,574
FHLMC MBS
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	111,745	115,525
Available-for-sale debt securities, 12 months or longer, Unrealized loss	13,241	11,324
Available-for-sale debt securities, Total, Fair value	111,745	115,525
Available-for-sale debt securities, Total, Unrealized loss	13,241	11,324
GNMA MBS
Available-for-sale debt securities:
Available-for-sale debt securities, Less than 12 months, Fair value	7,785	10,543
Available-for-sale debt securities, Less than 12 months, Unrealized loss	227	217
Available-for-sale debt securities, 12 months or longer, Fair value	35,109	31,681
Available-for-sale debt securities, 12 months or longer, Unrealized loss	3,312	2,782
Available-for-sale debt securities, Total, Fair value	42,894	42,224
Available-for-sale debt securities, Total, Unrealized loss	3,539	2,999
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	179,298	180,696
Available-for-sale debt securities, 12 months or longer, Unrealized loss	45,499	44,743
Available-for-sale debt securities, Total, Fair value	179,298	180,696
Available-for-sale debt securities, Total, Unrealized loss	$ 45,499	$ 44,743

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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