DERIVATIVE INSTRUMENTS - OFFSETTING OF ASSETS AND LIABILITIES (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Sep. 30, 2017
Financial commodity contracts
Derivative assets:
Amounts Presented in Balance Sheets	$ 375
Offsetting Derivative Instruments	(134)
Financial Collateral Received/Pledged	0
Net Amounts	241
Energy Services
Derivative assets:
Amounts Presented in Balance Sheets	39,915	$ 39,094
Offsetting Derivative Instruments	(21,934)	(16,294)
Financial Collateral Received/Pledged	(808)	(200)
Net Amounts	17,173	22,600
Derivative liabilities:
Amounts Presented in Balance Sheets	68,221	48,186
Offsetting Derivative Instruments	(21,395)	(16,294)
Financial Collateral Received/Pledged	(16,757)	(8,766)
Net Amounts	30,069	23,126
Energy Services | Physical commodity contracts
Derivative assets:
Amounts Presented in Balance Sheets	7,285	21,715
Offsetting Derivative Instruments	(1,903)	(2,173)
Financial Collateral Received/Pledged	(200)	(200)
Net Amounts	5,182	19,342
Derivative liabilities:
Amounts Presented in Balance Sheets	31,237	25,299
Offsetting Derivative Instruments	(1,903)	(2,173)
Financial Collateral Received/Pledged	0	0
Net Amounts	29,334	23,126
Energy Services | Financial commodity contracts
Derivative assets:
Amounts Presented in Balance Sheets	32,630	17,335
Offsetting Derivative Instruments	(20,031)	(14,121)
Financial Collateral Received/Pledged	(608)	0
Net Amounts	11,991	3,214
Derivative liabilities:
Amounts Presented in Balance Sheets	36,784	22,887
Offsetting Derivative Instruments	(19,492)	(14,121)
Financial Collateral Received/Pledged	(16,757)	(8,766)
Net Amounts	535	0
Energy Services | Foreign currency contracts
Derivative assets:
Amounts Presented in Balance Sheets		44
Offsetting Derivative Instruments		0
Financial Collateral Received/Pledged		0
Net Amounts		44
Derivative liabilities:
Amounts Presented in Balance Sheets	200
Offsetting Derivative Instruments	0
Financial Collateral Received/Pledged	0
Net Amounts	200
Natural Gas Distribution
Derivative assets:
Amounts Presented in Balance Sheets	463	151
Offsetting Derivative Instruments	(139)	(20)
Financial Collateral Received/Pledged	0	0
Net Amounts	324	131
Derivative liabilities:
Amounts Presented in Balance Sheets	160	9,688
Offsetting Derivative Instruments	(139)	(20)
Financial Collateral Received/Pledged	0	(1,149)
Net Amounts	21	8,519
Natural Gas Distribution | Physical commodity contracts
Derivative assets:
Amounts Presented in Balance Sheets	88	151
Offsetting Derivative Instruments	(5)	(20)
Financial Collateral Received/Pledged	0	0
Net Amounts	83	131
Derivative liabilities:
Amounts Presented in Balance Sheets	26	72
Offsetting Derivative Instruments	(5)	(20)
Financial Collateral Received/Pledged	0	0
Net Amounts	21	52
Natural Gas Distribution | Financial commodity contracts
Derivative liabilities:
Amounts Presented in Balance Sheets	134	1,149
Offsetting Derivative Instruments	(134)	0
Financial Collateral Received/Pledged	0	(1,149)
Net Amounts	0	0
Natural Gas Distribution | Interest rate contracts
Derivative liabilities:
Amounts Presented in Balance Sheets		8,467
Offsetting Derivative Instruments		0
Financial Collateral Received/Pledged		0
Net Amounts		$ 8,467
Home Services and Other
Derivative assets:
Amounts Presented in Balance Sheets	135
Offsetting Derivative Instruments	(14)
Financial Collateral Received/Pledged	0
Net Amounts	121
Derivative liabilities:
Amounts Presented in Balance Sheets	14
Offsetting Derivative Instruments	(14)
Financial Collateral Received/Pledged	0
Net Amounts	0
Home Services and Other | Physical commodity contracts
Derivative assets:
Amounts Presented in Balance Sheets	135
Offsetting Derivative Instruments	(14)
Financial Collateral Received/Pledged	0
Net Amounts	121
Home Services and Other | Interest rate contracts
Derivative liabilities:
Amounts Presented in Balance Sheets	14
Offsetting Derivative Instruments	(14)
Financial Collateral Received/Pledged	0
Net Amounts	$ 0