INFORMATION BY OPERATING SEGMENT (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Dec. 31, 2013 subsidiary	Dec. 31, 2012	Sep. 30, 2013
Segment Reporting [Abstract]
Number of entity subsidiaries	7
Operating Segment Information [Abstract]
Revenues from external customers	$ 468,610	$ 307,003
Total Operating Revenues	468,610	307,003
Operating Expenses [Abstract]
Natural and propane gas	241,787	136,515
Utilities Operating Expense, Other	62,322	39,651
Other Operation and Maintenance	62,322	39,651
Depreciation and amortization	20,026	10,965
Taxes, other than income taxes	28,589	14,806
Total Gas Utility Operating Expenses	352,724	201,937
Non-Regulated Gas Marketing	51,782	57,382
Gas Marketing	51,782	57,382
Other Cost and Expense, Operating	1,199	5,599
Total Operating Expenses	405,705	264,918
Operating Income (Loss)	62,905	42,085
Net Economic Earnings (Losses)	36,264	28,233
Total assets	3,206,730	1,942,155	3,125,386
Reconciliation of Consolidated Net Economic Earnings to Consolidated Net Income [Abstract]
Total Net Economic Earnings above	36,264	28,233
Add: Unrealized gain (loss) on energy-related derivative contracts, net of tax	(354)	439
Add: Realized gain (loss) on economic hedges prior to sale of the physical commodity, net of tax	6	(31)
Add: Acquisition, divestiture, and restructuring activities	386
Add: Acquisition, divestiture, and restructuring activities, net of tax		(2,257)
Add: Lower of cost or market inventory adjustments, net of tax	62	0
Net Income	35,592	25,568
Consolidation, Eliminations [Member] | Unallocated and Eliminations [Member]
Operating Segment Information [Abstract]
Revenues from external customers	0	0
Total Operating Revenues	(19,960)	(7,845)
Operating Expenses [Abstract]
Natural and propane gas	(19,766)	(7,818)
Utilities Operating Expense, Other	(194)	0
Depreciation and amortization	0	0
Taxes, other than income taxes	0	0
Total Gas Utility Operating Expenses	(19,960)	(7,818)
Non-Regulated Gas Marketing	0	0
Other Cost and Expense, Operating	0	(27)
Total Operating Expenses	(19,960)	(7,845)
Operating Income (Loss)	0	0
Net Economic Earnings (Losses)	0	0
Total assets	(161,533)	(181,137)
Reconciliation of Consolidated Net Economic Earnings to Consolidated Net Income [Abstract]
Total Net Economic Earnings above	0	0
Regulated Gas Distribution [Member] | Gas Utility [Member]
Operating Segment Information [Abstract]
Revenues from external customers	435,166	250,111
Total Operating Revenues	435,228	250,791
Operating Expenses [Abstract]
Natural and propane gas	261,553	144,333
Utilities Operating Expense, Other	62,516	39,651
Depreciation and amortization	20,026	10,965
Taxes, other than income taxes	28,589	14,806
Total Gas Utility Operating Expenses	372,684	209,755
Non-Regulated Gas Marketing	0	0
Other Cost and Expense, Operating	0	0
Total Operating Expenses	372,684	209,755
Operating Income (Loss)	62,544	41,036
Net Economic Earnings (Losses)	35,778	25,341
Total assets	3,084,134	1,809,722
Reconciliation of Consolidated Net Economic Earnings to Consolidated Net Income [Abstract]
Total Net Economic Earnings above	35,778	25,341
Other [Member] | Other [Member]
Operating Segment Information [Abstract]
Revenues from external customers	191	1,643
Total Operating Revenues	633	1,902
Operating Expenses [Abstract]
Natural and propane gas	0	0
Utilities Operating Expense, Other	0	0
Depreciation and amortization	0	0
Taxes, other than income taxes	0	0
Total Gas Utility Operating Expenses	0	0
Non-Regulated Gas Marketing	0	0
Other Cost and Expense, Operating	1,199	5,626
Total Operating Expenses	1,199	5,626
Operating Income (Loss)	(566)	(3,724)
Net Economic Earnings (Losses)	(336)	(389)
Total assets	126,890	124,967
Reconciliation of Consolidated Net Economic Earnings to Consolidated Net Income [Abstract]
Total Net Economic Earnings above	(336)	(389)
Non-Regulated Gas Marketing [Member] | Gas Marketing [Member]
Operating Segment Information [Abstract]
Revenues from external customers	33,253	55,249
Total Operating Revenues	52,709	62,155
Operating Expenses [Abstract]
Natural and propane gas	0	0
Utilities Operating Expense, Other	0	0
Depreciation and amortization	0	0
Taxes, other than income taxes	0	0
Total Gas Utility Operating Expenses	0	0
Non-Regulated Gas Marketing	51,782	57,382
Other Cost and Expense, Operating	0	0
Total Operating Expenses	51,782	57,382
Operating Income (Loss)	927	4,773
Net Economic Earnings (Losses)	822	3,281
Total assets	157,239	188,603
Reconciliation of Consolidated Net Economic Earnings to Consolidated Net Income [Abstract]
Total Net Economic Earnings above	822	3,281
Intersubsegment Eliminations [Member]
Operating Segment Information [Abstract]
Revenue from Related Parties	0	0
Intersubsegment Eliminations [Member] | Consolidation, Eliminations [Member] | Unallocated and Eliminations [Member]
Operating Segment Information [Abstract]
Revenue from Related Parties	(19,960)	(7,845)
Intersubsegment Eliminations [Member] | Regulated Gas Distribution [Member] | Gas Utility [Member]
Operating Segment Information [Abstract]
Revenue from Related Parties	62	680
Intersubsegment Eliminations [Member] | Other [Member] | Other [Member]
Operating Segment Information [Abstract]
Revenue from Related Parties	442	259
Intersubsegment Eliminations [Member] | Non-Regulated Gas Marketing [Member] | Gas Marketing [Member]
Operating Segment Information [Abstract]
Revenue from Related Parties	$ 19,456	$ 6,906