Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2016
Earnings Per Share, Basic and Diluted [Abstract]
Net Income	$ 85,280	$ 72,395	$ 155,574	$ 63,411	$ 64,691	$ 60,044	$ 58,814	$ 62,244	$ 376,660	$ 245,793	$ 248,867
Common share information:
Basic weighted average shares outstanding	77,261	77,247	77,218	77,283	77,602	77,597	77,814	78,413	77,252	77,856	79,416
Dilutive effect of stock options and restricted stock									333	399	318
Diluted weighted average shares outstanding	77,585	77,546	77,565	77,646	78,064	77,932	78,180	78,844	77,585	78,255	79,734
Basic earnings per share	$ 1.10	$ 0.94	$ 2.01	$ 0.82	$ 0.83	$ 0.77	$ 0.76	$ 0.79	$ 4.88	$ 3.16	$ 3.13
Diluted earnings per share	$ 1.10	$ 0.93	$ 2.01	$ 0.82	$ 0.83	$ 0.77	$ 0.75	$ 0.79	$ 4.85	$ 3.14	$ 3.12
Antidilutive stock options and restricted stock excluded from computation of earnings per share									41	32	0