SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Schedule of New Accounting Pronouncements (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use assets	$ 18,992
Operating lease liabilities	(6,387)
Operating lease liabilities, long-term	(16,822)
Retained earnings	$ (917,336)		$ (771,925)
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use assets		$ 15,633
Operating lease liabilities		(4,344)
Operating lease liabilities, long-term		(12,405)
Retained earnings		$ (1,116)