BUSINESS SEGMENT AND OTHER OPERATIONS DATA - RECONCILIATION OF SEGMENT ASSETS TO CONSOLIDATED (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014		Sep. 30, 2014
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ 3,444,292		$ 3,158,804
Operating Segments [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	3,436,840		3,135,362
Operating Segments [Member] | Natural Gas Distribution [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	2,236,569		2,143,684
Operating Segments [Member] | Energy Services [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	597,702		457,080
Operating Segments [Member] | Clean Energy Ventures [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	450,030		380,707
Operating Segments [Member] | Midstream [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	152,539		153,891
Home Services and Other [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	93,480		82,413
Eliminations [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ (86,028)	[1]	$ (58,971)	[1]

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