SECURITIES - Amortized cost and Fair values of held-to-maturity securities transferred from available-for-sale securities (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022	Mar. 31, 2022
Available-for-sale:
Amortized Cost	$ 527,144	$ 541,600
Debt securities held-to-maturity	450,313	478,801
U.S. government agency
Available-for-sale:
Amortized Cost	88,442	88,424
Debt securities held-to-maturity	76,050	78,696
Agency residential
Available-for-sale:
Amortized Cost	98,115	102,728
Debt securities held-to-maturity	88,834	96,258
Agency commercial
Available-for-sale:
Amortized Cost	301,243	308,281
Debt securities held-to-maturity	$ 247,765	$ 261,799
Debt Securities Transferred
Available-for-sale:
Amortized Cost			$ 114,850
Debt securities held-to-maturity			104,131
Debt Securities Transferred | U.S. government agency
Available-for-sale:
Amortized Cost			78,841
Debt securities held-to-maturity			71,048
Debt Securities Transferred | Agency residential
Available-for-sale:
Amortized Cost			8,175
Debt securities held-to-maturity			7,651
Debt Securities Transferred | Agency commercial
Available-for-sale:
Amortized Cost			27,834
Debt securities held-to-maturity			$ 25,432