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, 2013		Jun. 30, 2012		Jun. 30, 2013		Jun. 30, 2012
Derivative Financial Instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Beginning Balance	$ (16,606)	[1]	$ (68,754)	[1]	$ (19,664)	[1]	$ (5,410)	[1]
Total Gains/Losses, Realized and Included in Earnings	2,471	[1],[2]	10,392	[1],[3]	9,271	[1],[4]	36,526	[1],[5]
Total Gains/Losses Unrealized and Included in Other Comprehensive Income (Loss)	6,208	[1]	41,814	[1]	2,466	[1]	(47,664)	[1]
Transfer In/Out of Level 3	0	[1]	0	[1]	0	[1]	0	[1]
Ending Balance	$ (7,927)	[1]	$ (16,548)	[1]	$ (7,927)	[1]	$ (16,548)	[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, 2013.

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

[4] Amounts are reported in Operating Revenues in the Consolidated Statement of Income for the nine months ended June 30, 2013.

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