CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 87,016	$ 80,465
Other comprehensive income (loss), net of tax
Net unrealized holding gains (losses) on available-for-sale securities, net of tax	2,394	(373)
Amortization and unrealized gains (losses) on interest rate agreements, net of tax	13,942	12,264
Net unrealized gains (losses) on commodity cash flow hedges, net of tax	7,818	(365)
Total other comprehensive income	24,154	11,526
Total comprehensive income	$ 111,170	$ 91,991