SECURITIES - Available for Sale Investment Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Amortized Cost, Available for sale:
Within one year	$ 4,133
One to five years	46,363
Five to ten years	43,556
Beyond ten years	367,539
Total	461,591	$ 639,463
Estimated Fair Value, Available for sale:
Within one year	4,138
One to five years	46,402
Five to ten years	43,457
Beyond ten years	372,084
Estimated Fair Value	466,081	638,291
U.S. Treasury securities
Amortized Cost, Available for sale:
Total		50,833
Estimated Fair Value, Available for sale:
Estimated Fair Value		50,822
U.S. GSE securities
Amortized Cost, Available for sale:
Total		5,000
Estimated Fair Value, Available for sale:
Estimated Fair Value		4,995
State and municipal obligations
Amortized Cost, Available for sale:
Total	34,874	34,303
Estimated Fair Value, Available for sale:
Estimated Fair Value	36,504	34,964
U.S. GSE residential mortgage-backed securities
Amortized Cost, Available for sale:
Total	117,323	84,550
Estimated Fair Value, Available for sale:
Estimated Fair Value	118,876	84,691
U.S. GSE residential collateralized mortgage obligations
Amortized Cost, Available for sale:
Total	159,501	278,149
Estimated Fair Value, Available for sale:
Estimated Fair Value	161,582	277,851
U.S. GSE commercial mortgage-backed securities
Amortized Cost, Available for sale:
Total	13,179	13,656
Estimated Fair Value, Available for sale:
Estimated Fair Value	13,368	13,609
U.S. GSE commercial collateralized mortgage obligations
Amortized Cost, Available for sale:
Total	63,464	102,722
Estimated Fair Value, Available for sale:
Estimated Fair Value	64,792	104,156
Other asset backed securities
Amortized Cost, Available for sale:
Total	24,250	24,250
Estimated Fair Value, Available for sale:
Estimated Fair Value	23,894	23,401
Corporate bonds
Amortized Cost, Available for sale:
Total	49,000	46,000
Estimated Fair Value, Available for sale:
Estimated Fair Value	$ 47,065	$ 43,802

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27161-111563

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=121558606&loc=SL82898722-210454

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+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
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-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=121558606&loc=SL82898722-210454

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
-Topic 320
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-Section 45
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