Summary Of Significant Accounting Policies (Reclassification Out Of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Operating Revenues	$ 335,617	$ 339,815	$ 1,159,943	$ 1,459,851
Purchased Gas	23,477	27,038	147,168	344,728
Other Income	1,519	2,066	7,173	4,638
Income Before Income Taxes	17,026	(510,041)	(580,151)	(348,334)
Income Tax Expense	(8,740)	216,907	251,641	156,610
Net Income (Loss) Available for Common Stock	8,286	(293,134)	(328,510)	(191,724)
Amount Of Gain Or (Loss) Reclassified From Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income Before Income Taxes	58,373	50,875	177,167	129,270
Income Tax Expense	(24,514)	(21,800)	(68,283)	(54,807)
Net Income (Loss) Available for Common Stock	33,859	29,075	108,884	74,463
Amount Of Gain Or (Loss) Reclassified From Accumulated Other Comprehensive Income [Member] | Gains (Losses) on Securities Available for Sale [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other Income	0	0	388	0
Amount Of Gain Or (Loss) Reclassified From Accumulated Other Comprehensive Income [Member] | Commodity Contracts [Member] | Gains And Losses On Derivative Financial Instruments [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Operating Revenues	58,354	50,878	172,596	124,386
Purchased Gas	70	(3)	4,520	4,884
Foreign Currency Contracts [Member] | Amount Of Gain Or (Loss) Reclassified From Accumulated Other Comprehensive Income [Member] | Gains And Losses On Derivative Financial Instruments [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Operation and Maintenance	$ (51)	$ 0	$ (337)	$ 0