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				6 Months Ended
	Mar. 31, 2015		Mar. 31, 2014		Mar. 31, 2015		Mar. 31, 2014
Derivative Financial Instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Roll Forward]
Beginning Balance	$ 5,337	[1]	$ (1,842)	[1]	$ 1,368	[1]	$ (5,190)	[1]
Total Gains/Losses, Realized and Included in Earnings	(2,949)	[1],[2]	763	[1],[3]	(6,804)	[1],[4]	1,043	[1],[5]
Total Gains/Losses Unrealized and Included in Other Comprehensive Income (Loss)	2,438	[1]	(292)	[1]	10,262	[1]	2,776	[1]
Transfer In/Out of Level 3	0	[1]	0	[1]	0	[1]	0	[1]
Ending Balance	$ 4,826	[1]	$ (1,371)	[1]	$ 4,826	[1]	$ (1,371)	[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 March 31, 2015.

[3] Amounts are reported in Operating Revenues in the Consolidated Statement of Income for the three months ended March 31, 2014.

[4] Amounts are reported in Operating Revenues in the Consolidated Statement of Income for the six months ended March 31, 2015.

[5] Amounts are reported in Operating Revenues in the Consolidated Statement of Income for the six months ended March 31, 2014.