INVESTMENT SECURITIES - Amortized Cost and Fair Value of Available for Sale Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Amortized Cost
Due in one year or less	$ 76,191
Due from one year to five years	732,862
Due from five to ten years	23,108
Due after ten years	22,758
Mortgage-backed securities	686,223
Amortized Cost	1,541,142	$ 1,559,005
Estimated Fair Value
Due in one year or less	75,649
Due from one year to five years	722,272
Due from five to ten years	22,363
Due after ten years	20,997
Mortgage-backed securities	655,555
Estimated Fair Value	1,496,836	1,500,060
Amortized Cost
Due in one year or less	0
Due from one year to five years	0
Due from five to ten years	0
Due after ten years	31,905
Mortgage-backed securities	102,270
Amortized Cost	134,175	134,864
Estimated Fair Value
Due in one year or less	0
Due from one year to five years	0
Due from five to ten years	0
Due after ten years	27,330
Mortgage-backed securities	88,763
Estimated Fair Value	$ 116,093	$ 114,538