SECURITIES - Summary of Available for Sale Investment Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Available for sale:
Amortized Cost	$ 548,621	$ 639,463
Gross Unrealized Gains	10,557	4,225
Gross Unrealized Losses	(5,900)	(5,397)
Estimated Fair Value	553,278	638,291
U.S. Treasury securities
Available for sale:
Amortized Cost	59,980	50,833
Gross Unrealized Gains	19
Gross Unrealized Losses		(11)
Estimated Fair Value	59,999	50,822
U.S. GSE securities
Available for sale:
Amortized Cost		5,000
Gross Unrealized Losses		(5)
Estimated Fair Value		4,995
State and municipal obligations
Available for sale:
Amortized Cost	37,233	34,303
Gross Unrealized Gains	805	704
Gross Unrealized Losses	(92)	(43)
Estimated Fair Value	37,946	34,964
U.S. GSE residential mortgage-backed securities
Available for sale:
Amortized Cost	80,136	84,550
Gross Unrealized Gains	1,756	609
Gross Unrealized Losses	(238)	(468)
Estimated Fair Value	81,654	84,691
U.S. GSE residential collateralized mortgage obligations
Available for sale:
Amortized Cost	200,029	278,149
Gross Unrealized Gains	5,463	1,166
Gross Unrealized Losses		(1,464)
Estimated Fair Value	205,492	277,851
U.S. GSE commercial mortgage-backed securities
Available for sale:
Amortized Cost	16,683	13,656
Gross Unrealized Gains	366	23
Gross Unrealized Losses	0	(70)
Estimated Fair Value	17,049	13,609
U.S. GSE commercial collateralized mortgage obligations
Available for sale:
Amortized Cost	81,310	102,722
Gross Unrealized Gains	2,148	1,723
Gross Unrealized Losses	(78)	(289)
Estimated Fair Value	83,380	104,156
Other asset backed securities
Available for sale:
Amortized Cost	24,250	24,250
Gross Unrealized Gains	0
Gross Unrealized Losses	(1,698)	(849)
Estimated Fair Value	22,552	23,401
Corporate bonds
Available for sale:
Amortized Cost	49,000	46,000
Gross Unrealized Gains	0
Gross Unrealized Losses	(3,794)	(2,198)
Estimated Fair Value	$ 45,206	$ 43,802

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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