SECURITIES - Summary of Held to Maturity Investment Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Held to maturity:
Amortized Cost	$ 100,934	$ 133,638
Gross Unrealized Gains	3,986	1,731
Gross Unrealized Losses	(9)	(342)
Estimated Fair Value	104,911	135,027
State and municipal obligations
Held to maturity:
Amortized Cost	26,886	41,008
Gross Unrealized Gains	1,497	809
Gross Unrealized Losses	(9)
Estimated Fair Value	28,374	41,817
U.S. GSE residential mortgage-backed securities
Held to maturity:
Amortized Cost	6,822	8,142
Gross Unrealized Gains	229	5
Gross Unrealized Losses		(54)
Estimated Fair Value	7,051	8,093
U.S. GSE residential collateralized mortgage obligations
Held to maturity:
Amortized Cost	25,413	39,936
Gross Unrealized Gains	671	624
Gross Unrealized Losses		(62)
Estimated Fair Value	26,084	40,498
U.S. GSE commercial mortgage-backed securities
Held to maturity:
Amortized Cost	16,742	17,215
Gross Unrealized Gains	695	102
Gross Unrealized Losses		(82)
Estimated Fair Value	17,437	17,235
U.S. GSE commercial collateralized mortgage obligations
Held to maturity:
Amortized Cost	25,071	27,337
Gross Unrealized Gains	894	191
Gross Unrealized Losses		(144)
Estimated Fair Value	$ 25,965	$ 27,384

Amount of investment in debt security measured at amortized cost (held-to-maturity).

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Fair value of investment in debt security measured at amortized cost (held-to-maturity).

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