BUSINESS SEGMENT AND OTHER OPERATIONS DATA - RECONCILIATION OF SEGMENT ASSETS TO CONSOLIDATED (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014		Sep. 30, 2013
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ 3,161,210		$ 3,004,783
Corporate, Non-Segment [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	89,810		85,293
Operating Segments [Member] | Natural Gas Distribution [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	2,157,317		2,094,940
Operating Segments [Member] | Energy Services [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	546,010		468,096
Operating Segments [Member] | Clean Energy Ventures [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	312,258		253,663
Operating Segments [Member] | Midstream [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	153,050		153,536
Operating Segments [Member] | Subtotal [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	3,168,635		2,970,235
Intercompany/Eliminations [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ (97,235)	[1]	$ (50,745)	[1]

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