BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES - Schedule of Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Apr. 30, 2018	May 01, 2017	Apr. 30, 2017	May 01, 2016	Apr. 30, 2016	Apr. 30, 2015
Accounting Policies [Abstract]
Cash and cash equivalents	$ 13,792	$ 11,891	$ 0	$ 28,819	$ 0		$ 0
Restricted cash	5,464	4,225		27,981
Total cash, cash equivalents and restricted cash	$ 19,256	$ 16,116	$ 56,800	$ 56,800	$ 71,508	$ 71,508	$ 60,033