Accumulated Other Comprehensive Income Components (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), beginning balance	$ 38,878	$ (47,607)
Other comprehensive income before reclassifications	21,890	8,059
Amounts reclassified from accumulated other comprehensive income	2,264	3,467
Net current-period other comprehensive income	24,154	11,526
Accumulated other comprehensive income (loss), ending balance	63,032	(36,081)
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), beginning balance	5,448	5,661
Other comprehensive income before reclassifications	2,394	(373)
Amounts reclassified from accumulated other comprehensive income	0	0
Net current-period other comprehensive income	2,394	(373)
Accumulated other comprehensive income (loss), ending balance	7,842	5,288
Accumulated Net Gain (Loss) from Interest Rate Hedges [Member] [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), beginning balance	37,906	(44,273)
Other comprehensive income before reclassifications	13,270	11,945
Amounts reclassified from accumulated other comprehensive income	672	319
Net current-period other comprehensive income	13,942	12,264
Accumulated other comprehensive income (loss), ending balance	51,848	(32,009)
Accumulated Net Gain (Loss) from Commodity Contracts Cash Flow Hedges [Member] [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), beginning balance	(4,476)	(8,995)
Other comprehensive income before reclassifications	6,226	(3,513)
Amounts reclassified from accumulated other comprehensive income	1,592	3,148
Net current-period other comprehensive income	7,818	(365)
Accumulated other comprehensive income (loss), ending balance	$ 3,342	$ (9,360)