Fair Value Measurements (Fair Value Measurements Using Unobservable Inputs (Level 3)) (Details) (Derivative Financial Instruments [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2012		Jun. 30, 2011
Derivative Financial Instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Beginning Balance	$ (68,754)	[1]	$ (71,913)	[1]	$ (5,410)	[1]	$ (16,483)	[1]
Total Gains/Losses, Realized and Included in Earnings	10,392	[1],[2]	15,377	[1],[3]	36,526	[1],[2]	28,545	[1],[3]
Total Gains/Losses Unrealized and Included in Other Comprehensive Income (Loss)	41,814	[1]	6,083	[1]	(47,664)	[1]	(62,515)	[1]
Transfer In/Out of Level 3	0	[1]	0	[1]	0	[1]	0	[1]
Ending Balance	$ (16,548)	[1]	$ (50,453)	[1]	$ (16,548)	[1]	$ (50,453)	[1]

[1] Derivative Financial Instruments are shown on a net basis.

[2] Amounts are reported in Operating Revenues in the Consolidated Statement of Income for the three months ended June 30, 2012.

[3] Amounts are reported in Operating Revenues in the Consolidated Statement of Income for the three months ended June 30, 2011