INCOME TAXES - Deferred (Details) - USD ($) $ in Thousands	12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Deferred tax assets:
Stock-based compensation	$ 805	$ 5,979
Net operating losses	1,933	5,341
Foreign tax credits	11,172	19,869
Other	7,346	7,382
Total deferred tax assets	21,256	38,571
Valuation allowance	(12,811)	(6,474)
Net deferred tax assets	8,445	32,097
Deferred tax liabilities:
Mineral property basis	(74,274)	(122,870)
Unrealized foreign exchange gains	(664)	(1,097)
2019 Notes	(2,631)	(8,634)
Investment in Peak Gold joint venture	(4,359)	(5,475)
Other	(213)	(595)
Total deferred tax liabilities	(82,141)	(138,671)
Total net deferred taxes	(73,696)	(106,574)
Net operating loss carry forwards	$ 7,100	$ 32,100
Tax carryforward period	20 years