ACCRUED EXPENSES - Information Regarding Accrued Expenses (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016
Accrued Liabilities [Abstract]
Accrued sales tax	$ 16,559	$ 12,686
Accrued compensation and related sales commissions	2,071	3,100
Accrued professional fees	2,847	936
Accrued taxes and filing fees	209	160
Accrued other	1,672	2,475
Total accrued expenses	23,358	19,357
Less: accrued expenses, current	(23,258)	(19,291)	$ (18,508)	$ (16,623)	$ (12,217)	$ (11,873)	$ (8,792)	$ (7,541)	$ (8,135)
Accrued expenses, noncurrent	$ 100	$ 66	$ 66	$ 65	$ 62	$ 53	$ 52	$ 52	$ 11