MARKETABLE SECURITIES - Contractual Maturities of Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Amortized Cost
Due within one year	$ 5,095
Due after one year through five years	51,142
Due after five years through ten years	51,401
Due after ten years	82,571
Available-for-sale debt securities, amortized cost basis	371,189	$ 210,212
Estimated Fair Value
Due within one year	5,115
Due after one year through five years	51,724
Due after five years through ten years	52,805
Due after ten years	83,594
Available-for-sale debt securities, estimated fair value	377,062	212,716
Mortgage-backed securities
Amortized Cost
Available-for-sale debt securities, amortized cost basis	93,979
Available-for-sale debt securities, amortized cost basis	93,979	83,967
Estimated Fair Value
Available-for-sale debt securities, estimated fair value	96,420
Available-for-sale debt securities, estimated fair value	96,420	84,182
Collateralized mortgage obligations
Amortized Cost
Available-for-sale debt securities, amortized cost basis	87,001
Available-for-sale debt securities, amortized cost basis	87,001	89,798
Estimated Fair Value
Available-for-sale debt securities, estimated fair value	87,404
Available-for-sale debt securities, estimated fair value	$ 87,404	$ 90,927

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=118939692&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=118942338&loc=SL82898722-210454

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+ References

Reference 1: 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=118942338&loc=SL82898722-210454

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