Summary Of Significant Accounting Policies (Schedule Of Computation Of Basic And Diluted Net Income Per Share) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Accounting Policies [Abstract]
Net income	$ 94,021	$ 79,473	$ 69,641	$ 68,048	$ 76,231	$ 68,178	$ 63,412	$ 69,493	$ 311,183	$ 277,314	$ 275,186
Weighted average shares outstanding - basic	73,817	74,812	75,508	77,438	78,353	78,516	78,601	78,789	75,395	78,565	79,135
Dilutive effect of common shares from stock options and restricted stock units									697	571	645
Weighted average shares outstanding - diluted	74,366	75,369	76,244	77,822	78,674	78,864	79,114	79,278	76,092	79,136	79,780
Basic net income per share (USD per share)	$ 1.27	$ 1.06	$ 0.92	$ 0.88	$ 0.97	$ 0.87	$ 0.81	$ 0.88	$ 4.13	$ 3.53	$ 3.48
Diluted net income per share (USD per share)	$ 1.26	$ 1.05	$ 0.91	$ 0.87	$ 0.97	$ 0.86	$ 0.80	$ 0.88	$ 4.09	$ 3.50	$ 3.45