BUSINESS SEGMENT AND OTHER OPERATIONS DATA - RECONCILIATION OF SEGMENT ASSETS TO CONSOLIDATED (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015		Sep. 30, 2014
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ 3,333,381		$ 3,158,804
Operating Segments [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	3,227,342		3,135,362
Operating Segments [Member] | Natural Gas Distribution [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	2,268,272		2,143,684
Operating Segments [Member] | Energy Services [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	334,123		457,080
Operating Segments [Member] | Clean Energy Ventures [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	473,136		380,707
Operating Segments [Member] | Midstream [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	151,811		153,891
Home Services and Other [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	167,610		82,413
Eliminations [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ (61,571)	[1]	$ (58,971)	[1]

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