SECURITIES - Summary of Held to Maturity Investment Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Held to maturity:
Amortized Cost	$ 133,638	$ 160,163
Gross Unrealized Gains	1,731	457
Gross Unrealized Losses	(342)	(3,828)
Estimated Fair Value	135,027	156,792
State and municipal obligations
Held to maturity:
Amortized Cost	41,008	53,540
Gross Unrealized Gains	809	290
Gross Unrealized Losses	0	(276)
Estimated Fair Value	41,817	53,554
U.S. GSE residential mortgage-backed securities
Held to maturity:
Amortized Cost	8,142	9,688
Gross Unrealized Gains	5	0
Gross Unrealized Losses	(54)	(336)
Estimated Fair Value	8,093	9,352
U.S. GSE residential collateralized mortgage obligations
Held to maturity:
Amortized Cost	39,936	48,244
Gross Unrealized Gains	624	163
Gross Unrealized Losses	(62)	(1,130)
Estimated Fair Value	40,498	47,277
U.S. GSE commercial mortgage-backed securities
Held to maturity:
Amortized Cost	17,215	19,098
Gross Unrealized Gains	102	4
Gross Unrealized Losses	(82)	(620)
Estimated Fair Value	17,235	18,482
U.S. GSE commercial collateralized mortgage obligations
Held to maturity:
Amortized Cost	27,337	29,593
Gross Unrealized Gains	191	0
Gross Unrealized Losses	(144)	(1,466)
Estimated Fair Value	$ 27,384	$ 28,127

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

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

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Amount of accumulated unrealized loss on 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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