SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Recent Accounting Pronouncements (Details) $ in Thousands	Dec. 31, 2018 USD ($) lease	Dec. 31, 2017 USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Equity investment portfolio balance		$ 3,000
Right of use leased asset	$ 5,572	$ 5,572
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Right of use leased asset	$ 8,500
Number of leased facilities | lease	15