SECURITIES - Summary of Held to Maturity Investment Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Held to maturity:
Amortized Cost	$ 144,716	$ 160,163
Gross Unrealized Gains	1,825	457
Gross Unrealized Losses	(1,061)	(3,828)
Estimated Fair Value	145,480	156,792
State and municipal obligations
Held to maturity:
Amortized Cost	42,582	53,540
Gross Unrealized Gains	927	290
Gross Unrealized Losses	(1)	(276)
Estimated Fair Value	43,508	53,554
U.S. GSE residential mortgage-backed securities
Held to maturity:
Amortized Cost	8,900	9,688
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(109)	(336)
Estimated Fair Value	8,791	9,352
U.S. GSE residential collateralized mortgage obligations
Held to maturity:
Amortized Cost	45,961	48,244
Gross Unrealized Gains	655	163
Gross Unrealized Losses	(315)	(1,130)
Estimated Fair Value	46,301	47,277
U.S. GSE commercial mortgage-backed securities
Held to maturity:
Amortized Cost	18,721	19,098
Gross Unrealized Gains	125	4
Gross Unrealized Losses	(70)	(620)
Estimated Fair Value	18,776	18,482
U.S. GSE commercial collateralized mortgage obligations
Held to maturity:
Amortized Cost	28,552	29,593
Gross Unrealized Gains	118	0
Gross Unrealized Losses	(566)	(1,466)
Estimated Fair Value	$ 28,104	$ 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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