SECURITIES - Summary of Available for Sale Investment Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Available for sale:
Amortized Cost	$ 445,987	$ 639,463
Gross Unrealized Gains	6,775	4,225
Gross Unrealized Losses	(2,402)	(5,397)
Estimated Fair Value	450,360	638,291
U.S. Treasury securities
Available for sale:
Amortized Cost		50,833
Gross Unrealized Losses		(11)
Estimated Fair Value		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	40,448	34,303
Gross Unrealized Gains	1,650	704
Gross Unrealized Losses	(10)	(43)
Estimated Fair Value	42,088	34,964
U.S. GSE residential mortgage-backed securities
Available for sale:
Amortized Cost	111,398	84,550
Gross Unrealized Gains	1,843	609
Gross Unrealized Losses	(6)	(468)
Estimated Fair Value	113,235	84,691
U.S. GSE residential collateralized mortgage obligations
Available for sale:
Amortized Cost	127,369	278,149
Gross Unrealized Gains	1,661	1,166
Gross Unrealized Losses	(226)	(1,464)
Estimated Fair Value	128,804	277,851
U.S. GSE commercial mortgage-backed securities
Available for sale:
Amortized Cost	24,920	13,656
Gross Unrealized Gains	140	23
Gross Unrealized Losses	(253)	(70)
Estimated Fair Value	24,807	13,609
U.S. GSE commercial collateralized mortgage obligations
Available for sale:
Amortized Cost	61,102	102,722
Gross Unrealized Gains	1,286	1,723
Gross Unrealized Losses	(52)	(289)
Estimated Fair Value	62,336	104,156
Other asset backed securities
Available for sale:
Amortized Cost	24,250	24,250
Gross Unrealized Losses	(300)	(849)
Estimated Fair Value	23,950	23,401
Corporate
Available for sale:
Amortized Cost	56,500	46,000
Gross Unrealized Gains	195
Gross Unrealized Losses	(1,555)	(2,198)
Estimated Fair Value	$ 55,140	$ 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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