SECURITIES - Held to Maturity Investment Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Amortized Cost, Held to maturity:
Within one year	$ 1,885
One to five years	23,140
Five to ten years	11,535
Beyond ten years	49,140
Total	85,700	$ 133,638
Estimated Fair Value, Held to maturity:
Within one year	1,902
One to five years	24,452
Five to ten years	12,144
Beyond ten years	50,827
Estimated Fair Value	89,325	135,027
State and municipal obligations
Amortized Cost, Held to maturity:
Total	23,715	41,008
Estimated Fair Value, Held to maturity:
Estimated Fair Value	25,121	41,817
U.S. GSE residential mortgage-backed securities
Amortized Cost, Held to maturity:
Total	6,272	8,142
Estimated Fair Value, Held to maturity:
Estimated Fair Value	6,499	8,093
U.S. GSE residential collateralized mortgage obligations
Amortized Cost, Held to maturity:
Total	18,511	39,936
Estimated Fair Value, Held to maturity:
Estimated Fair Value	18,991	40,498
U.S. GSE commercial mortgage-backed securities
Amortized Cost, Held to maturity:
Total	13,069	17,215
Estimated Fair Value, Held to maturity:
Estimated Fair Value	13,694	17,235
U.S. GSE commercial collateralized mortgage obligations
Amortized Cost, Held to maturity:
Total	24,133	27,337
Estimated Fair Value, Held to maturity:
Estimated Fair Value	$ 25,020	$ 27,384