CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2011
Statement of Comprehensive Income [Abstract]
Net income	$ 350,224	$ 272,171	$ 271,674
Other comprehensive gains (losses), net of tax
Unrealized holding loss	(244)	(3,094)	(1,934)
Reclassification adjustment for loss included in net income	1,774	1,610	407
Total other comprehensive gain (loss)	1,530	(1,484)	(1,527)
Comprehensive income	$ 351,754	$ 270,687	$ 270,147