REVENUE - Impact of Adoption of ASC 606 (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Mar. 31, 2019	Mar. 31, 2018	Jul. 01, 2018	Jun. 30, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Prepaid expenses and other current assets	$ 2,878			$ 1,278			$ 2,878	$ 1,278	$ 1,180	$ 929
Other assets	1,922						1,922
Deferred revenue	1,322						1,322
Accumulated deficit	(253,859)			(231,052)			(253,859)	(231,052)	(232,372)	(232,748)
License and transaction fees	37,646			33,592			105,574	90,383
Selling, general and administrative	11,156			9,629			31,537	25,558
Net loss	(4,510)	$ (10,657)	$ (6,320)	(3,223)	$ (4,194)	$ (2,171)	(21,487)	(9,588)
Under Legacy Guidance
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Prepaid expenses and other current assets	2,615						2,615			929
Other assets	608						608
Deferred revenue	313						313
Accumulated deficit	(254,427)						(254,427)			$ (232,748)
Selling, general and administrative	11,214						31,609
Net loss	(4,640)						(21,677)
Service
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
License and transaction fees	31,630			$ 25,381			90,438	$ 68,292
Service | Under Legacy Guidance
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
License and transaction fees	31,559						90,320
ASC 606 | Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Prepaid expenses and other current assets	(263)						(263)		251
Other assets	(1,314)						(1,314)
Deferred revenue	(1,009)						(1,009)
Accumulated deficit	(568)						(568)		$ 376
Selling, general and administrative	58						72
Net loss	(130)						(190)
ASC 606 | Service | Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
License and transaction fees	$ (71)						$ (118)