REVENUE - TIMING OF REVENUE RECOGNITION - BALANCE SHEET (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Sep. 30, 2022	Mar. 31, 2022	Sep. 30, 2021
Disaggregation of Revenue [Line Items]
Billed	$ 194,453	$ 222,297
Customers' credit balances and deposits	(25,521)	(33,246)	$ (20,284)	$ (32,586)
Customers accounts receivables & Customers' credit balances and deposits	214,972	202,820
Billed
Disaggregation of Revenue [Line Items]
Billed	194,453	222,297	273,313	212,838
Unbilled
Disaggregation of Revenue [Line Items]
Billed	46,040	13,769	$ 56,270	$ 10,351
Operating Segments | Natural Gas Distribution
Disaggregation of Revenue [Line Items]
Customers' credit balances and deposits	(25,516)	(33,246)
Customers accounts receivables & Customers' credit balances and deposits	159,779	56,076
Operating Segments | Natural Gas Distribution | Billed
Disaggregation of Revenue [Line Items]
Billed	142,275	78,508
Operating Segments | Natural Gas Distribution | Unbilled
Disaggregation of Revenue [Line Items]
Billed	43,020	10,814
Operating Segments | Clean Energy Ventures
Disaggregation of Revenue [Line Items]
Customers' credit balances and deposits	0	0
Customers accounts receivables & Customers' credit balances and deposits	8,937	8,521
Operating Segments | Clean Energy Ventures | Billed
Disaggregation of Revenue [Line Items]
Billed	5,917	5,566
Operating Segments | Clean Energy Ventures | Unbilled
Disaggregation of Revenue [Line Items]
Billed	3,020	2,955
Operating Segments | Energy Services
Disaggregation of Revenue [Line Items]
Customers' credit balances and deposits	0	0
Customers accounts receivables & Customers' credit balances and deposits	37,280	129,199
Operating Segments | Energy Services | Billed
Disaggregation of Revenue [Line Items]
Billed	37,280	129,199
Operating Segments | Energy Services | Unbilled
Disaggregation of Revenue [Line Items]
Billed	0	0
Operating Segments | Storage and Transportation
Disaggregation of Revenue [Line Items]
Customers' credit balances and deposits	(5)	0
Customers accounts receivables & Customers' credit balances and deposits	7,085	7,012
Operating Segments | Storage and Transportation | Billed
Disaggregation of Revenue [Line Items]
Billed	7,090	7,012
Operating Segments | Storage and Transportation | Unbilled
Disaggregation of Revenue [Line Items]
Billed	0	0
Home Services and Other
Disaggregation of Revenue [Line Items]
Customers' credit balances and deposits	0	0
Customers accounts receivables & Customers' credit balances and deposits	1,891	2,012
Home Services and Other | Billed
Disaggregation of Revenue [Line Items]
Billed	1,891	2,012
Home Services and Other | Unbilled
Disaggregation of Revenue [Line Items]
Billed	$ 0	$ 0