LEASES - Operating Lease Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Lease Liabilities - ASC 842
2020	$ 2,230
2021	2,230
2022	2,230
2023	2,378
2024	2,453
Thereafter	1,839
Total lease payments	13,360
Less: Imputed interest	(1,857)
Present value of lease liabilities	11,503
Operating cash flow payments	$ 2,230
Operating Lease Liabilities - ASC 840
2019		$ 2,230
2020		2,230
2021		2,230
2022		2,230
2023		2,378
Thereafter		4,292
Total lease payments		15,590
Deferred rent		3,468
Rent expense		$ 1,808	$ 1,808

For a classified balance sheet, the cumulative difference between the rental income or payments required by a lease agreement and the rental income or expense recognized on a straight-line basis, or other systematic and rational basis more representative of the time pattern in which use or benefit is granted or derived from the leased property, expected to be recognized in income or expense, by the lessor or lessee, respectively, more than one year after the balance sheet date.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.26(c))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 20
-Section 25
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=77902458&loc=d3e39927-112707