Fair Value Measurements (Fair Value Measurements Using Unobservable Inputs (Level 3)) (Details) - Derivative Financial Instruments [Member] - USD ($) $ in Thousands		12 Months Ended
		Sep. 30, 2016		Sep. 30, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Balance, Beginning of Year	[1]	$ 1,791		$ 1,368
Total Gains/Losses, Realized and Included in Earnings	[1]	(2,002)	[2]	(12,738)	[3]
Total Gains/Losses, Unrealized and Included in Other Comprehensive Income (Loss)	[1]	211		13,161
Transfer In/(Out) of Level 3	[1]	0		0
Balance, End of Year	[1]	$ 0		$ 1,791

[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 year ended September 30, 2016.

[3] Amounts are reported in Operating Revenues in the Consolidated Statement of Income for the year ended September 30, 2015.