SECURITIES - Summary of Held to Maturity Investment Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Held to maturity:
Amortized Cost	$ 139,729	$ 160,163
Gross Unrealized Gains	2,176	457
Gross Unrealized Losses	(402)	(3,828)
Estimated Fair Value	141,503	156,792
State and municipal obligations
Held to maturity:
Amortized Cost	42,512	53,540
Gross Unrealized Gains	928	290
Gross Unrealized Losses		(276)
Estimated Fair Value	43,440	53,554
U.S. GSE residential mortgage-backed securities
Held to maturity:
Amortized Cost	8,514	9,688
Gross Unrealized Gains	3	0
Gross Unrealized Losses	(58)	(336)
Estimated Fair Value	8,459	9,352
U.S. GSE residential collateralized mortgage obligations
Held to maturity:
Amortized Cost	43,881	48,244
Gross Unrealized Gains	739	163
Gross Unrealized Losses	(264)	(1,130)
Estimated Fair Value	44,356	47,277
U.S. GSE commercial mortgage-backed securities
Held to maturity:
Amortized Cost	17,407	19,098
Gross Unrealized Gains	209	4
Gross Unrealized Losses	(15)	(620)
Estimated Fair Value	17,601	18,482
U.S. GSE commercial collateralized mortgage obligations
Held to maturity:
Amortized Cost	27,415	29,593
Gross Unrealized Gains	297	0
Gross Unrealized Losses	(65)	(1,466)
Estimated Fair Value	$ 27,647	$ 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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