CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 97,595	$ 87,016
Other comprehensive income (loss), net of tax
Net unrealized holding gains (losses) on available-for-sale securities, net of tax	(1,067)	2,394
Amortization and unrealized gains (losses) on interest rate agreements, net of tax	(51,787)	13,942
Net unrealized gains (losses) on commodity cash flow hedges, net of tax	(28,952)	7,818
Total other comprehensive income (loss)	(81,806)	24,154
Total comprehensive income (loss)	$ 15,789	$ 111,170