CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 38,768	$ 31,132	$ 235,658	$ 208,750
Other comprehensive income (loss), net of tax
Net unrealized holding gains (losses) on available-for-sale securities, net of tax	(348)	(888)	(921)	2,059
Amortization and unrealized gains (losses) on interest rate agreements, net of tax	31,079	(31,328)	66,852	(17,019)
Net unrealized gains (losses) on commodity cash flow hedges, net of tax	(3,508)	17,830	4,965	(4,060)
Total other comprehensive income	27,223	(14,386)	70,896	(19,020)
Total comprehensive income	$ 65,991	$ 16,746	$ 306,554	$ 189,730