DERIVATIVE INSTRUMENTS - OFFSETTING OF ASSETS AND LIABILITIES (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Sep. 30, 2019
Energy Services
Derivative assets:
Amounts Presented in Balance Sheets	$ 54,120	$ 32,080
Offsetting Derivative Instruments	(25,572)	(22,553)
Financial Collateral Received/Pledged	(200)	(200)
Net Amounts	28,348	9,327
Derivative liabilities:
Amounts Presented in Balance Sheets	61,535	75,629
Offsetting Derivative Instruments	(25,572)	(22,553)
Financial Collateral Received/Pledged	(1,671)	(15,516)
Net Amounts	34,292	37,560
Energy Services | Physical commodity contracts
Derivative assets:
Amounts Presented in Balance Sheets	15,159	8,557
Offsetting Derivative Instruments	(3,569)	(2,906)
Financial Collateral Received/Pledged	(200)	(200)
Net Amounts	11,390	5,451
Derivative liabilities:
Amounts Presented in Balance Sheets	37,628	40,181
Offsetting Derivative Instruments	(3,569)	(2,906)
Financial Collateral Received/Pledged	0	0
Net Amounts	34,059	37,275
Energy Services | Financial commodity contracts
Derivative assets:
Amounts Presented in Balance Sheets	38,946	23,522
Offsetting Derivative Instruments	(21,988)	(19,646)
Financial Collateral Received/Pledged	0	0
Net Amounts	16,958	3,876
Derivative liabilities:
Amounts Presented in Balance Sheets	23,783	35,162
Offsetting Derivative Instruments	(21,988)	(19,646)
Financial Collateral Received/Pledged	(1,671)	(15,516)
Net Amounts	124	0
Energy Services | Foreign currency contracts
Derivative assets:
Amounts Presented in Balance Sheets	15	1
Offsetting Derivative Instruments	(15)	(1)
Financial Collateral Received/Pledged	0	0
Net Amounts	0	0
Derivative liabilities:
Amounts Presented in Balance Sheets	124	286
Offsetting Derivative Instruments	(15)	(1)
Financial Collateral Received/Pledged	0	0
Net Amounts	109	285
Natural Gas Distribution
Derivative assets:
Amounts Presented in Balance Sheets	26	449
Offsetting Derivative Instruments	(2)	(391)
Financial Collateral Received/Pledged	0	0
Net Amounts	24	58
Derivative liabilities:
Amounts Presented in Balance Sheets	525	815
Offsetting Derivative Instruments	(2)	(391)
Financial Collateral Received/Pledged	(363)	(188)
Net Amounts	160	236
Natural Gas Distribution | Physical commodity contracts
Derivative assets:
Amounts Presented in Balance Sheets	26	67
Offsetting Derivative Instruments	(2)	(9)
Financial Collateral Received/Pledged	0	0
Net Amounts	24	58
Derivative liabilities:
Amounts Presented in Balance Sheets	162	245
Offsetting Derivative Instruments	(2)	(9)
Financial Collateral Received/Pledged	0	0
Net Amounts	160	236
Natural Gas Distribution | Financial commodity contracts
Derivative assets:
Amounts Presented in Balance Sheets		382
Offsetting Derivative Instruments		(382)
Financial Collateral Received/Pledged		0
Net Amounts		0
Derivative liabilities:
Amounts Presented in Balance Sheets	363	570
Offsetting Derivative Instruments	0	(382)
Financial Collateral Received/Pledged	(363)	(188)
Net Amounts	$ 0	$ 0