Condensed Consolidated Statements Of Changes In Shareholders' Equity (USD $) In Thousands	Common Stock [Member]	Paid-In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]	Total
Beginning Balance at Sep. 30, 2011	$ 64,960	$ 145,084	$ 1,444,270	$ (1,527)	$ 1,652,787
Beginning Balance (in shares) at Sep. 30, 2011	64,960
Net income			65,468		65,468
Other comprehensive loss				(208)	(208)
Restricted stock awards	188	(188)
Restricted stock awards (in shares)	188
Exercise of employee stock options	4	75			79
Exercise of employee stock options (in shares)	4
Stock option and restricted stock award compensation expense		1,790			1,790
Ending Balance at Dec. 31, 2011	$ 65,152	$ 146,761	$ 1,509,738	$ (1,735)	$ 1,719,916
Ending Balance (in shares) at Dec. 31, 2011	65,152