ACCOUNTING POLICIES - Recent Accounting Pronouncements (Details) - USD ($) $ in Thousands	3 Months Ended								6 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Mar. 31, 2018	Mar. 31, 2017	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
(Provision) benefit for income taxes		$ (20)	$ 157	$ (28)	$ (26)	$ (23)	$ (23)	$ (23)	$ 129	$ (46)	$ 109	$ (69)	$ (262)	$ 101	$ (95)
Deferred tax asset, current						$ 0	$ 0	$ 0		$ 0		$ 0				$ 2,300
Deferred tax assets, noncurrent																$ 2,300
Accounting Standards Update 2016-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
(Provision) benefit for income taxes	$ 31													$ 67