BUSINESS SEGMENT AND OTHER OPERATIONS DATA, RECONCILIATION OF SEGMENT ASSETS TO CONSOLIDATED (Details) (USD $) In Thousands	Jun. 30, 2011		Sep. 30, 2010
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ 2,573,956		$ 2,563,133
Categorized Business Segments [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	2,529,627		2,496,807
Natural Gas Distribution [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	1,906,403		1,904,545
Energy Services [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	442,980		432,380
Midstream Assets [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	162,516		159,882
Clean Energy Ventures [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	17,728		0
Retail and Other [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	72,598		85,864
Business Intersegment, Eliminations [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ (28,269)	[1]	$ (19,538)	[1]

[1] Consists of transactions between subsidiaries that are eliminated and reclassified in consolidation.