ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Cash and Cash Equivalents (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Cash and Cash Equivalents [Line Items]
Credit card receivables	$ 1.6	$ 2.0
Cash and cash equivalents held in bank accounts in foreign countries	19.9	$ 30.6
South Korea
Cash and Cash Equivalents [Line Items]
Net assets	$ 14.4