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
	Dec. 31, 2011		Dec. 31, 2010
Derivative Financial Instruments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Beginning Balance	$ (5,410)	[1]	$ (16,483)	[1]
Total Gains/Losses, Realized and Unrealized, Included in Earnings	12,612	[1],[2]	3,602	[1],[3]
Total Gains/Losses, Realized and Unrealized, Included in Other Comprehensive Income (Loss)	(61,975)	[1]	(24,526)	[1]
Transfer In/Out of Level 3	0	[1]	0	[1]
Ending Balance	$ (54,773)	[1]	$ (37,407)	[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 December 31, 2011.

[3] Amounts are reported in Operating Revenues in the Consolidated Statement of Income for the three months ended December 31, 2010.