Consolidated Statements of Changes in Stockholder's Equity - USD ($) $ in Thousands	Common Shares	Additional Paid-In Capital	Accumulated (Losses) Earnings	Noncontrolling Interests	Total
Balance at Jun. 30, 2019	$ 655	$ 2,201,773	$ (65,747)	$ 33,772	$ 2,170,453
Balance (in shares) at Jun. 30, 2019	65,440,492
Increase (Decrease) in Stockholders' Equity
Stock-based compensation and related share issuances		4,025			4,025
Stock-based compensation and related share issuances (in shares)	71,756
Distributions from (to) non-controlling interests		3,300		(723)	2,577
Net income (loss) and comprehensive income (loss)			150,329	(2,750)	147,579
Dividends declared			(54,099)		(54,099)
Balance at Mar. 31, 2020	$ 655	2,209,098	30,483	30,299	2,270,535
Balance (in shares) at Mar. 31, 2020	65,512,248
Balance at Dec. 31, 2019	$ 655	2,205,364	10,290	30,905	2,247,214
Balance (in shares) at Dec. 31, 2019	65,496,004
Increase (Decrease) in Stockholders' Equity
Stock-based compensation and related share issuances		3,134			3,134
Stock-based compensation and related share issuances (in shares)	16,244
Distributions from (to) non-controlling interests		600		(344)	256
Net income (loss) and comprehensive income (loss)			38,554	(262)	38,292
Dividends declared			(18,361)		(18,361)
Balance at Mar. 31, 2020	$ 655	2,209,098	30,483	30,299	2,270,535
Balance (in shares) at Mar. 31, 2020	65,512,248
Balance at Jun. 30, 2020	$ 655	2,210,429	61,133	29,902	2,302,119
Balance (in shares) at Jun. 30, 2020	65,531,288
Increase (Decrease) in Stockholders' Equity
Stock-based compensation and related share issuances	$ 1	2,810			2,811
Stock-based compensation and related share issuances (in shares)	19,157
Sale of Peak Gold JV interest		(10,829)		(16,218)	(27,047)
Distributions to non-controlling interests				(880)	(880)
Net income (loss) and comprehensive income (loss)			220,855	1	220,856
Dividends declared			(57,734)		(57,734)
Balance at Mar. 31, 2021	$ 656	2,202,410	224,254	12,805	2,440,125
Balance (in shares) at Mar. 31, 2021	65,550,445
Balance at Dec. 31, 2020	$ 656	2,201,076	189,910	13,037	2,404,679
Balance (in shares) at Dec. 31, 2020	65,548,415
Increase (Decrease) in Stockholders' Equity
Stock-based compensation and related share issuances		1,334			1,334
Stock-based compensation and related share issuances (in shares)	2,030
Distributions to non-controlling interests				(399)	(399)
Net income (loss) and comprehensive income (loss)			54,026	167	54,193
Dividends declared			(19,682)		(19,682)
Balance at Mar. 31, 2021	$ 656	$ 2,202,410	$ 224,254	$ 12,805	$ 2,440,125
Balance (in shares) at Mar. 31, 2021	65,550,445