DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES - Exchange-Traded/Cleared Derivatives (Details) MMBTU in Thousands	12 Months Ended
	Sep. 30, 2018 MMBTU $ / MMBTU
Gas Utility | Natural gas contracts | Fiscal 2022
Derivative [Line Items]
MMBtu (millions) | MMBTU	0
Avg. Price Per MMBtu | $ / MMBTU	0.00
Gas Utility | Natural gas contracts | Fiscal 2023
Derivative [Line Items]
MMBtu (millions) | MMBTU	0
Avg. Price Per MMBtu | $ / MMBTU	0.00
Gas Marketing | Natural gas contracts | Fiscal 2022
Derivative [Line Items]
MMBtu (millions) | MMBTU	250
Avg. Price Per MMBtu | $ / MMBTU	2.98
Gas Marketing | Natural gas contracts | Fiscal 2023
Derivative [Line Items]
MMBtu (millions) | MMBTU	10
Avg. Price Per MMBtu | $ / MMBTU	2.86
Short | Gas Utility | Natural gas contracts | Fiscal 2019
Derivative [Line Items]
MMBtu (millions) | MMBTU	0
Avg. Price Per MMBtu | $ / MMBTU	0.00
Short | Gas Utility | Natural gas contracts | Fiscal 2020
Derivative [Line Items]
MMBtu (millions) | MMBTU	0
Avg. Price Per MMBtu | $ / MMBTU	0.00
Short | Gas Utility | Natural gas contracts | Fiscal 2021
Derivative [Line Items]
MMBtu (millions) | MMBTU	0
Avg. Price Per MMBtu | $ / MMBTU	0.00
Short | Gas Utility | ICE open daily swap positions | Fiscal 2019
Derivative [Line Items]
MMBtu (millions) | MMBTU	0
Avg. Price Per MMBtu | $ / MMBTU	0.00
Short | Gas Utility | ICE Open basis swap positions | Fiscal 2019
Derivative [Line Items]
MMBtu (millions) | MMBTU	0
Avg. Price Per MMBtu | $ / MMBTU	0.00
Short | Gas Utility | ICE Open basis swap positions | Fiscal 2020
Derivative [Line Items]
MMBtu (millions) | MMBTU	0
Avg. Price Per MMBtu | $ / MMBTU	0.00
Short | Gas Marketing | Natural gas contracts | Fiscal 2019
Derivative [Line Items]
MMBtu (millions) | MMBTU	7,870
Avg. Price Per MMBtu | $ / MMBTU	3.04
Short | Gas Marketing | Natural gas contracts | Fiscal 2020
Derivative [Line Items]
MMBtu (millions) | MMBTU	2,000
Avg. Price Per MMBtu | $ / MMBTU	2.93
Short | Gas Marketing | Natural gas contracts | Fiscal 2021
Derivative [Line Items]
MMBtu (millions) | MMBTU	140
Avg. Price Per MMBtu | $ / MMBTU	2.94
Short | Gas Marketing | ICE open daily swap positions | Fiscal 2019
Derivative [Line Items]
MMBtu (millions) | MMBTU	2,540
Avg. Price Per MMBtu | $ / MMBTU	2.95
Short | Gas Marketing | ICE Open basis swap positions | Fiscal 2019
Derivative [Line Items]
MMBtu (millions) | MMBTU	52,480
Avg. Price Per MMBtu | $ / MMBTU	0.23
Short | Gas Marketing | ICE Open basis swap positions | Fiscal 2020
Derivative [Line Items]
MMBtu (millions) | MMBTU	3,800
Avg. Price Per MMBtu | $ / MMBTU	0.25
Long | Gas Utility | Natural gas contracts | Fiscal 2019
Derivative [Line Items]
MMBtu (millions) | MMBTU	24,120
Avg. Price Per MMBtu | $ / MMBTU	2.80
Long | Gas Utility | Natural gas contracts | Fiscal 2020
Derivative [Line Items]
MMBtu (millions) | MMBTU	2,680
Avg. Price Per MMBtu | $ / MMBTU	2.69
Long | Gas Utility | Natural gas contracts | Fiscal 2021
Derivative [Line Items]
MMBtu (millions) | MMBTU	0
Avg. Price Per MMBtu | $ / MMBTU	0.00
Long | Gas Utility | ICE open daily swap positions | Fiscal 2019
Derivative [Line Items]
MMBtu (millions) | MMBTU	0
Avg. Price Per MMBtu | $ / MMBTU	0.00
Long | Gas Utility | ICE Open basis swap positions | Fiscal 2019
Derivative [Line Items]
MMBtu (millions) | MMBTU	0
Avg. Price Per MMBtu | $ / MMBTU	0.00
Long | Gas Utility | ICE Open basis swap positions | Fiscal 2020
Derivative [Line Items]
MMBtu (millions) | MMBTU	0
Avg. Price Per MMBtu | $ / MMBTU	0.00
Long | Gas Utility | ICE Open basis swap positions | Fiscal 2022
Derivative [Line Items]
MMBtu (millions) | MMBTU	0
Avg. Price Per MMBtu | $ / MMBTU	0.00
Long | Gas Utility | ICE Open basis swap positions | Fiscal 2023
Derivative [Line Items]
MMBtu (millions) | MMBTU	0
Avg. Price Per MMBtu | $ / MMBTU	0.00
Long | Gas Marketing | Natural gas contracts | Fiscal 2019
Derivative [Line Items]
MMBtu (millions) | MMBTU	9,270
Avg. Price Per MMBtu | $ / MMBTU	2.89
Long | Gas Marketing | Natural gas contracts | Fiscal 2020
Derivative [Line Items]
MMBtu (millions) | MMBTU	2,110
Avg. Price Per MMBtu | $ / MMBTU	2.85
Long | Gas Marketing | Natural gas contracts | Fiscal 2021
Derivative [Line Items]
MMBtu (millions) | MMBTU	550
Avg. Price Per MMBtu | $ / MMBTU	2.87
Long | Gas Marketing | ICE open daily swap positions | Fiscal 2019
Derivative [Line Items]
MMBtu (millions) | MMBTU	570
Avg. Price Per MMBtu | $ / MMBTU	2.92
Long | Gas Marketing | ICE Open basis swap positions | Fiscal 2019
Derivative [Line Items]
MMBtu (millions) | MMBTU	49,990
Avg. Price Per MMBtu | $ / MMBTU	0.64
Long | Gas Marketing | ICE Open basis swap positions | Fiscal 2020
Derivative [Line Items]
MMBtu (millions) | MMBTU	3,180
Avg. Price Per MMBtu | $ / MMBTU	0.68
Long | Gas Marketing | ICE Open basis swap positions | Fiscal 2022
Derivative [Line Items]
MMBtu (millions) | MMBTU	920
Avg. Price Per MMBtu | $ / MMBTU	0.52
Long | Gas Marketing | ICE Open basis swap positions | Fiscal 2023
Derivative [Line Items]
MMBtu (millions) | MMBTU	160
Avg. Price Per MMBtu | $ / MMBTU	0.52