Discontinued Operations (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2012	Mar. 31, 2011	Sep. 30, 2011
Discontinued Operation Income Loss From Discontinued Operation Disclosures Abstract
Operating revenues	$ 26,374	$ 35,790	$ 49,825	$ 59,523
Purchased gas cost	17,026	24,636	31,977	39,533
Gross profit	9,348	11,154	17,848	19,990
Operating expenses	4,275	4,431	8,449	8,447
Operating income	5,073	6,723	9,399	11,543
Miscellaneous (expense)	38	32	86	65
Income from discontinued operations before income taxes	5,035	6,691	9,313	11,478
Income tax expense	1,834	2,642	3,393	4,532
Income (loss) from discontinued operations	3,201	4,049	5,920	6,946
Disposal Group Including Discontinued Operation Balance Sheet Disclosures Abstract
Net plant, property & equipment	126,587		126,587		127,577
Gas stored underground	6,517		6,517		11,931
Other current assets	515		515		786
Deferred charges and other assets	49		49		277
Assets held for sale	133,668		133,668		140,571
Accounts payable	5,404		5,404		1,917
Other current liabilities	6,857		6,857		4,877
Regulatory cost of removal	7,687		7,687		10,498
Deferred credits and other liabilities	872		872		1,153
Liabilities held for sale	$ 20,820		$ 20,820		$ 18,445
Other Discontinued Operations Disclosures [Abstract]
Disposal Group Sales Price			124000000