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, 2013	$ 2,207,371	$ 64,057	$ 183,390	$ 1,961,405	$ (1,481)
Beginning Balance (in shares) at Sep. 30, 2013		64,057
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	83,397			83,397
Other comprehensive loss	(362)				(362)
Restricted stock awards	0	127	(127)
Restricted stock awards (in shares)		127
Exercise of employee stock options	823	24	799
Exercise of employee stock options (in shares)	24	24
Stock option and restricted stock award compensation expense	3,354		3,354
Ending Balance at Dec. 31, 2013	$ 2,294,583	$ 64,208	$ 187,416	$ 2,044,802	$ (1,843)
Ending Balance (in shares) at Dec. 31, 2013		64,208