Summary Of Significant Accounting Policies (Schedule Of Basic And Diluted Net Income Per Common Share Calculations) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended						9 Months Ended
	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Mar. 31, 2019	Mar. 31, 2018
Accounting Policies [Abstract]
Net income	$ 30,604	$ 47,907	$ 39,028	$ 27,621	$ 45,920	$ 29,386	$ 117,539	$ 102,927
Net income available to participating securities	(52)			(58)			(212)	(206)
Net income available to common shareholders	$ 30,552			$ 27,563			$ 117,327	$ 102,721
Weighted average common shares outstanding - basic (in shares)	27,448			27,405			27,436	27,399
Incremental share effect from:
Nonparticipating restricted stock (in shares)	1			2			3	3
Stock-settled stock appreciation rights (in shares)	100			51			104	54
Weighted average common shares outstanding - diluted (in shares)	27,549			27,458			27,543	27,456
Net income per common share - basic (in dollars per share)	$ 1.11			$ 1.01			$ 4.28	$ 3.75
Net income per common share - diluted (in dollars per share)	$ 1.11			$ 1.00			$ 4.26	$ 3.74