Summary of Significant Accounting Policies (Schedule Of Computation Of Basic And Diluted Net Income Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016
Accounting Policies [Abstract]
Net income	$ 93,138	$ 75,415	$ 187,356	$ 165,131
Weighted average shares outstanding - basic	64,479	67,549	64,841	68,557
Dilutive effect of common shares from stock options and restricted stock units	549	255	548	324
Weighted average shares outstanding - diluted	65,028	67,804	65,389	68,881
Basic net income per share (dollars per share)	$ 1.44	$ 1.12	$ 2.89	$ 2.41
Diluted net income per share (dollars per share)	$ 1.43	$ 1.11	$ 2.87	$ 2.40