BUSINESS SEGMENT AND OTHER OPERATIONS DATA - RECONCILIATION OF SEGMENT ASSETS TO CONSOLIDATED (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014		Sep. 30, 2013
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ 3,105,907		$ 3,004,783
Operating Segments [Member] | Natural Gas Distribution [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	2,123,260		2,094,940
Operating Segments [Member] | Energy Services [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	463,597		468,096
Operating Segments [Member] | Clean Energy Ventures [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	362,240		253,663
Operating Segments [Member] | Midstream [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	153,214		153,536
Operating Segments [Member] | Subtotal [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	3,102,311		2,970,235
Retail and Other [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	85,148		85,293
Eliminations [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ (81,552)	[1]	$ (50,745)	[1]

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