Condensed Consolidated Statement Of Changes In Shareholders' Equity (USD $) In Thousands	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
Net income	72,831			72,831
Other comprehensive gain	372				372
Restricted stock awards		142	(142)
Restricted stock awards (in shares)		142
Exercise of employee stock options	653	38	615
Exercise of employee stock options (in shares)	38	38
Stock option and restricted stock award compensation expense	3,048		3,048
Ending Balance at Dec. 31, 2012	$ 2,016,326	$ 65,632	$ 164,061	$ 1,789,272	$ (2,639)
Ending Balance (in shares) at Dec. 31, 2012		65,632