ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Schedule of Cash and Cash Equivalents (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Cash And Cash Equivalents, Resticted Cash And Restricted Cash Equivalents [Roll Forward]
Cash and cash equivalents, at carrying value	$ 37,936	$ 37,682		$ 28,687
Restricted cash, current	1,515	1,514		1,510
Restricted cash, noncurrent	7,598	7,565		6,429
Cash, cash equivalents, restricted cash and restricted cash equivalents	$ 47,049	$ 46,761	$ 37,894	$ 36,626