Consolidated Statements of Changes in Equity - USD ($) $ in Thousands	Common Shares	Exchangeable Shares	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Earnings	Noncontrolling Interests	Total
Balance at Jun. 30, 2014	$ 646	$ 16,718	$ 2,147,650	$ (160)	$ 189,871	$ 17,832	$ 2,372,557
Balance (in shares) at Jun. 30, 2014	64,578,401	379,857
Issuance of common stock for:
Exchange of exchangeable shares	$ 3	$ (16,718)	16,715
Exchange of exchangeable shares (in shares)	379,857	(379,857)
Peak Gold joint venture						45,700	45,700
Stock-based compensation and related share issuances	$ 1		6,278				6,279
Stock-based compensation and related share issuances (in shares)	75,289
Net income					51,965	713	52,678
Other comprehensive income (loss)				(3,132)			(3,132)
Distribution to non-controlling interests						(1,440)	(1,440)
Dividends declared					(56,715)		(56,715)
Balance at Jun. 30, 2015	$ 650		2,170,643	(3,292)	185,121	62,805	2,415,927
Balance (in shares) at Jun. 30, 2015	65,033,547
Issuance of common stock for:
Stock-based compensation and related share issuances	$ 1		9,138				9,139
Stock-based compensation and related share issuances (in shares)	60,403
Net income					(77,149)	(5,289)	(82,438)
Other comprehensive income (loss)				3,292			3,292
Distribution to non-controlling interests						(647)	(647)
Dividends declared					(59,388)		(59,388)
Balance at Jun. 30, 2016	$ 651		2,179,781		48,584	56,869	2,285,885
Balance (in shares) at Jun. 30, 2016	65,093,950
Issuance of common stock for:
Stock-based compensation and related share issuances	$ 1		8,533				8,534
Stock-based compensation and related share issuances (in shares)	85,577
Net income					101,530	(9,105)	92,425
Other comprehensive income (loss)				879			879
Distribution to non-controlling interests						(2,877)	(2,877)
Dividends declared					(62,064)		(62,064)
Non-controlling interest assignment			(2,518)				(2,518)
Balance at Jun. 30, 2017	$ 652		$ 2,185,796	$ 879	$ 88,050	$ 44,887	$ 2,320,264
Balance (in shares) at Jun. 30, 2017	65,179,527