BUSINESS SEGMENT AND OTHER OPERATIONS DATA - RECONCILIATION OF SEGMENT ASSETS TO CONSOLIDATED (Details) - USD ($) $ in Thousands		Dec. 31, 2015	Sep. 30, 2015
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets		$ 3,477,238	$ 3,284,357
Natural Gas Distribution [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets		2,357,063	2,305,293
Energy Services [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets		310,364	260,021
Clean Energy Ventures [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets		597,897	504,885
Midstream [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets		191,292	182,007
Subtotal [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets		3,456,616	3,252,206
Home Services and Other [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets		90,012	88,880
Intercompany Assets [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	[1]	$ (69,390)	$ (56,729)

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