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	$ 243,194	$ 216,717	$ 207,601
Other comprehensive income (loss), net of tax [Abstract]
Net unrealized holding gains (losses) on available-for-sale securities, net of tax of $(186), $1,881 and $(953)	(213)	3,103	(1,647)
Amortization and unrealized gain (loss) on interest rate agreements, net of tax of $47,236, $(5,388) and $(16,850)	82,179	(10,116)	(28,689)
Net unrealized gains on commodity cash flow hedges, net of tax of $2,889, $5,029 and $3,355	4,519	7,866	5,248
Total other comprehensive income (loss)	86,485	853	(25,088)
Total comprehensive income	$ 329,679	$ 217,570	$ 182,513