Condensed Consolidated Statements Of Stockholders' Equity - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-In Capital [Member]	Treasury Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Total
Beginning balance at Jun. 30, 2018	$ 571	$ 1,450,821	$ (1,600,412)	$ 2,432,328	$ (224,328)	$ 2,058,980
Beginning balance, shares at Jun. 30, 2018	184,316,000		(41,636,000)
Common stock issued on exercise of options		513				513
Common stock issued on exercise of options, shares	12,000
Common stock issued on vesting of restricted stock units, net of shares withheld for tax		(141)				(141)
Common stock issued on vesting of restricted stock units, net of shares withheld for tax, shares	2,000
Treasury stock purchases	$ (1)		$ (22,844)			(22,845)
Treasury stock purchases, shares			(200,000)
Stock-based compensation costs		12,476				12,476
Other comprehensive income					(12,872)	(12,872)
Net income				105,738		105,738
Dividends declared				(52,794)		(52,794)
Ending balance at Sep. 30, 2018	$ 570	1,463,669	$ (1,623,256)	2,296,473	(237,200)	1,900,256
Ending balance, shares at Sep. 30, 2018	184,330,000		(41,836,000)
Beginning balance at Jun. 30, 2018	$ 571	1,450,821	$ (1,600,412)	2,432,328	(224,328)	$ 2,058,980
Beginning balance, shares at Jun. 30, 2018	184,316,000		(41,636,000)
Common stock issued on employee stock purchase plan, shares						129,000
Treasury stock purchases						$ (22,800)
Treasury stock purchases, shares						(200,000)
Net income						$ 335,791
Ending balance at Mar. 31, 2019	$ 573	1,476,099	$ (1,623,256)	2,420,731	(252,818)	2,021,329
Ending balance, shares at Mar. 31, 2019	185,182,000		(41,836,000)
Cumulative effect of change in accounting standards				(188,799)		(188,799)
Beginning balance at Sep. 30, 2018	$ 570	1,463,669	$ (1,623,256)	2,296,473	(237,200)	1,900,256
Beginning balance, shares at Sep. 30, 2018	184,330,000		(41,836,000)
Common stock issued on exercise of options		1,263				1,263
Common stock issued on exercise of options, shares	36,000
Common stock issued on vesting of restricted stock units, net of shares withheld for tax	$ 2	(27,343)				(27,341)
Common stock issued on vesting of restricted stock units, net of shares withheld for tax, shares	623,000
Common stock issued on employee stock purchase plan	$ 1	10,575				10,576
Common stock issued on employee stock purchase plan, shares	129,000
Stock-based compensation costs		12,541				12,541
Other comprehensive income					(13,117)	(13,117)
Net income				124,639		124,639
Dividends declared				(52,773)		(52,773)
Ending balance at Dec. 31, 2018	$ 573	1,460,705	$ (1,623,256)	2,368,339	(250,317)	1,956,044
Ending balance, shares at Dec. 31, 2018	185,118,000		(41,836,000)
Common stock issued on exercise of options		2,896				2,896
Common stock issued on exercise of options, shares	55,000
Common stock issued on vesting of restricted stock units, net of shares withheld for tax		(330)				(330)
Common stock issued on vesting of restricted stock units, net of shares withheld for tax, shares	9,000
Stock-based compensation costs		12,828				12,828
Other comprehensive income					(2,501)	(2,501)
Net income				105,416		105,416
Dividends declared				(53,024)		(53,024)
Ending balance at Mar. 31, 2019	$ 573	1,476,099	$ (1,623,256)	2,420,731	(252,818)	2,021,329
Ending balance, shares at Mar. 31, 2019	185,182,000		(41,836,000)
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	185,491,000		41,836,000
Common stock issued on exercise of options		5,609				5,609
Common stock issued on exercise of options, shares	110,000
Common stock issued on vesting of restricted stock units, net of shares withheld for tax		(327)				(327)
Common stock issued on vesting of restricted stock units, net of shares withheld for tax, shares	4,000
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	185,605,000		41,836,000
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	185,491,000		41,836,000
Common stock issued on exercise of options, shares						260,666
Common stock issued on employee stock purchase plan, shares						137,000
Treasury stock purchases						$ (1,600,000)
Treasury stock purchases, shares						(41,800,000)
Net income						$ 443,839
Ending balance at Mar. 31, 2020	$ 579	1,533,905	$ (1,623,256)	2,711,639	(366,436)	2,256,431
Ending balance, shares at Mar. 31, 2020	186,499,000		(41,836,000)
Beginning balance at Sep. 30, 2019	$ 575	1,530,011	$ (1,623,256)	2,500,506	(290,585)	2,117,251
Beginning balance, shares at Sep. 30, 2019	185,605,000		41,836,000
Common stock issued on exercise of options		6,498				6,498
Common stock issued on exercise of options, shares	117,000
Common stock issued on vesting of restricted stock units, net of shares withheld for tax	$ 3	(40,764)				(40,761)
Common stock issued on vesting of restricted stock units, net of shares withheld for tax, shares	576,000
Common stock issued on employee stock purchase plan		12,190				12,190
Common stock issued on employee stock purchase plan, shares	137,000
Stock-based compensation costs		14,057				14,057
Other comprehensive income					44,467	44,467
Net income				160,554		160,554
Dividends declared				(56,150)		(56,150)
Ending balance at Dec. 31, 2019	$ 578	1,521,992	$ (1,623,256)	2,604,910	(246,118)	2,258,106
Ending balance, shares at Dec. 31, 2019	186,435,000		(41,836,000)
Common stock issued on exercise of options	$ 1	1,815				1,816
Common stock issued on exercise of options, shares	34,000
Common stock issued on vesting of restricted stock units, net of shares withheld for tax		(4,014)				(4,014)
Common stock issued on vesting of restricted stock units, net of shares withheld for tax, shares	30,000
Stock-based compensation costs		14,112				14,112
Other comprehensive income					(120,318)	(120,318)
Net income				163,137		163,137
Dividends declared				(56,408)		(56,408)
Ending balance at Mar. 31, 2020	$ 579	$ 1,533,905	$ (1,623,256)	$ 2,711,639	$ (366,436)	$ 2,256,431
Ending balance, shares at Mar. 31, 2020	186,499,000		(41,836,000)