Fair Value Measurements (Fair Value Measurements Using Unobservable Inputs (Level 3)) (Details) - Derivative Financial Instruments [Member] - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Mar. 31, 2015		Mar. 31, 2016		Mar. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Roll Forward]
Beginning Balance	[1]	$ 5,337		$ 1,791		$ 1,368
Total Gains/Losses, Realized and Included in Earnings	[1]	(2,949)	[2]	(2,002)	[3]	(6,804)	[4]
Total Gains/Losses Unrealized and Included in Other Comprehensive Income (Loss)	[1]	2,438		211		10,262
Transfer In/Out of Level 3	[1]	0		0		0
Ending Balance	[1]	$ 4,826		$ 0		$ 4,826

[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 six months ended March 31, 2016.

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