Condensed Consolidated Statements Of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Common Stock [Member]	Additional Paid-In Capital [Member]	Treasury Stock [Member]	Retained Earnings [Member] Cumulative Effect Of Change In Accounting Standards [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Cumulative Effect Of Change In Accounting Standards [Member]	Total
Beginning balance at Jun. 30, 2019	$ 575	$ 1,511,473	$ (1,623,256)		$ 2,436,410	$ (253,009)		$ 2,072,193
Beginning balance, shares at Jun. 30, 2019	185,491		(41,836)
Common stock issued on exercise of options (note 11)		5,609						5,609
Common stock issued on exercise of options (note 11), shares	110
Common stock issued on vesting of restricted stock units, net of shares withheld for tax (note 11)		(327)						(327)
Common stock issued on vesting of restricted stock units, net of shares withheld for tax (note 11), shares	4
Stock-based compensation costs		13,256						13,256
Other comprehensive income						(37,576)		(37,576)
Net income					120,148			120,148
Dividends declared					(56,052)			(56,052)
Ending balance at Sep. 30, 2019	$ 575	1,530,011	$ (1,623,256)		2,500,506	(290,585)		2,117,251
Ending balance, shares at Sep. 30, 2019	185,605		(41,836)
Beginning balance at Jun. 30, 2020	$ 580	1,570,694	$ (1,623,256)		2,832,991	(283,982)		2,497,027
Beginning balance, shares at Jun. 30, 2020	186,723		41,836
Common stock issued on exercise of options (note 11)		1,026						1,026
Common stock issued on exercise of options (note 11), shares	18
Common stock issued on vesting of restricted stock units, net of shares withheld for tax (note 11)		227						227
Common stock issued on vesting of restricted stock units, net of shares withheld for tax (note 11), shares	3
Stock-based compensation costs		16,071						16,071
Other comprehensive income						43,791		43,791
Net income					178,372			178,372
Dividends declared					(56,511)			(56,511)
Ending balance at Sep. 30, 2020	$ 580	$ 1,588,018	$ (1,623,256)	$ (1,143)	$ 2,953,709	$ (240,191)	$ (1,143)	$ 2,678,860
Ending balance, shares at Sep. 30, 2020	186,744		41,836