REVENUE - TIMING OF REVENUE RECOGNITION - BALANCE SHEET (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Customer accounts receivable:
Billed	$ 212,838	$ 134,173	$ 139,263
Unbilled revenues	10,351	9,226	6,510
Customers' credit balances and deposits	(32,586)	(25,934)	$ (27,116)
Customers accounts receivables & Customers' credit balances and deposits	190,603	117,465
Operating Segments | Natural Gas Distribution
Customer accounts receivable:
Billed	54,514	52,134
Unbilled revenues	8,427	7,842
Customers' credit balances and deposits	(32,586)	(25,934)
Customers accounts receivables & Customers' credit balances and deposits	30,355	34,042
Operating Segments | Clean Energy Ventures
Customer accounts receivable:
Billed	5,534	5,282
Unbilled revenues	1,924	1,384
Customers' credit balances and deposits	0	0
Customers accounts receivables & Customers' credit balances and deposits	7,458	6,666
Operating Segments | Energy Services
Customer accounts receivable:
Billed	147,087	70,457
Unbilled revenues	0	0
Customers' credit balances and deposits	0	0
Customers accounts receivables & Customers' credit balances and deposits	147,087	70,457
Operating Segments | Storage and Transportation
Customer accounts receivable:
Billed	3,956	3,905
Unbilled revenues	0	0
Customers' credit balances and deposits	0	0
Customers accounts receivables & Customers' credit balances and deposits	3,956	3,905
Home Services and Other
Customer accounts receivable:
Billed	1,747	2,395
Unbilled revenues	0	0
Customers' credit balances and deposits	0	0
Customers accounts receivables & Customers' credit balances and deposits	$ 1,747	$ 2,395