Share Capital, Option Plans and Share-Based Payments - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Dividends declared per common share (in dollars per share)	$ 0.132	$ 0.115	$ 0.264	$ 0.23
Payments of dividends	$ 34,800	$ 27,900	$ 69,828	$ 55,650
Preference shares issued (in shares)	0		0
Common shares repurchased (in shares)			0	0
Issuance of treasury stock (in shares)	379,111	341,588	387,443	349,922