Condensed Consolidated Statement Of Changes In Shareholders' Equity (USD $) In Thousands, unless otherwise specified	Total	Common Stock	Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Loss
Beginning Balance at Sep. 30, 2012	$ 1,939,422	$ 65,452	$ 160,540	$ 1,716,441	$ (3,011)
Beginning Balance (in shares) at Sep. 30, 2012		65,452
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	248,331			248,331
Other comprehensive gain	1,319				1,319
Restricted stock awards	0	162	(162)
Restricted stock awards (in shares)		162
Exercise of employee stock options	6,451	338	6,113
Exercise of employee stock options (in shares)	338	338
Stock option and restricted stock award compensation expense	10,418		10,418
Repurchase and retirement of common shares	(107,260)	(2,000)		(105,260)
Repurchase and retirement of shares (in shares)		(2,000)
Ending Balance at Jun. 30, 2013	$ 2,098,681	$ 63,952	$ 176,909	$ 1,859,512	$ (1,692)
Ending Balance (in shares) at Jun. 30, 2013		63,952