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, 2012		Dec. 31, 2011
Derivative Financial Instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Beginning Balance	$ (19,664)	[1]	$ (5,410)	[1]
Total Gains/Losses, Realized and Included in Earnings	2,261	[1],[2]	12,612	[1],[2]
Total Gains/Losses Unrealized and Included in Other Comprehensive Income (Loss)	3,314	[1]	(61,975)	[1]
Transfer In/Out of Level 3	0	[1]	0	[1]
Ending Balance	$ (14,089)	[1]	$ (54,773)	[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, 2012.