BUSINESS SEGMENT AND OTHER OPERATIONS DATA, RECONCILIATION OF SEGMENT ASSETS TO CONSOLIDATED (Details) - USD ($) $ in Thousands		Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets		$ 3,727,082	$ 3,284,357	$ 3,125,388
Operating Segments
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets		3,704,641	3,252,206	3,114,281
Operating Segments | Natural Gas Distribution
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets		2,525,060	2,305,293	2,142,407
Operating Segments | Clean Energy Ventures
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets		665,696	504,885	380,275
Operating Segments | Energy Services
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets		327,626	260,021	437,708
Operating Segments | Midstream
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets		186,259	182,007	153,891
Home Services and Other
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets		110,340	88,880	77,578
Eliminations
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	[1]	$ (87,899)	$ (56,729)	$ (66,471)

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