Earnings Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2011
Net Income	$ 47,669	$ 45,996	$ 40,505	$ 42,475	$ 43,327	$ 36,657	$ 38,525	$ 36,475	$ 176,645	$ 154,984	$ 137,471
Common share information:
Weighted average shares outstanding for basic earnings per share	85,845	86,120	86,084	86,109	86,595	86,824	86,572	86,403	86,040	86,599	85,948
Dilutive effect of stock options and restricted stock									579	688	739
Weighted average shares outstanding for diluted earnings per share	86,525	86,705	86,639	86,605	87,051	87,592	87,371	87,134	86,619	87,287	86,687
Basic earnings per share	$ 0.56	$ 0.53	$ 0.47	$ 0.49	$ 0.50	$ 0.42	$ 0.45	$ 0.42	$ 2.05	$ 1.79	$ 1.60
Diluted earnings per share	$ 0.55	$ 0.53	$ 0.47	$ 0.49	$ 0.50	$ 0.42	$ 0.44	$ 0.42	$ 2.04	$ 1.78	$ 1.59
Antidilutive stock options and restricted stock excluded from computation of earnings per share									0	0	12