SECURITIES - Summary of Held to Maturity Investment Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Held to maturity:
Amortized Cost	$ 160,163	$ 180,866
Gross Unrealized Gains	457	1,293
Gross Unrealized Losses	(3,828)	(2,274)
Estimated Fair Value	156,792	179,885
State and municipal obligations
Held to maturity:
Amortized Cost	53,540	60,762
Gross Unrealized Gains	290	972
Gross Unrealized Losses	(276)	(64)
Estimated Fair Value	53,554	61,670
U.S. GSE residential mortgage-backed securities
Held to maturity:
Amortized Cost	9,688	11,424
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(336)	(261)
Estimated Fair Value	9,352	11,163
U.S. GSE residential collateralized mortgage obligations
Held to maturity:
Amortized Cost	48,244	54,250
Gross Unrealized Gains	163	244
Gross Unrealized Losses	(1,130)	(666)
Estimated Fair Value	47,277	53,828
U.S. GSE commercial mortgage-backed securities
Held to maturity:
Amortized Cost	19,098	22,953
Gross Unrealized Gains	4	77
Gross Unrealized Losses	(620)	(438)
Estimated Fair Value	18,482	22,592
U.S. GSE commercial collateralized mortgage obligations
Held to maturity:
Amortized Cost	29,593	31,477
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1,466)	(845)
Estimated Fair Value	$ 28,127	$ 30,632

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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