CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Statement of Comprehensive Income [Abstract]
Net income	$ 340,822	$ 350,224	$ 272,171
Derivative financial instruments:
Unrealized holding gain (loss)	4,208	(244)	(3,094)
Reclassification adjustment for loss included in net income	834	1,774	1,610
Total other comprehensive income (loss)	5,042	1,530	(1,484)
Comprehensive income	$ 345,864	$ 351,754	$ 270,687