REVENUE - TIMING OF REVENUE RECOGNITION - BALANCE SHEET (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Sep. 30, 2021	Jun. 30, 2021	Sep. 30, 2020
Customer accounts receivable
Billed	$ 268,043	$ 212,838	$ 205,482	$ 134,173
Unbilled revenues	15,032	10,351	12,663	9,226
Customers' credit balances and deposits	(22,216)	(32,586)	$ (22,699)	$ (25,934)
Customers accounts receivables & Customers' credit balances and deposits	260,859	190,603
Operating Segments | Natural Gas Distribution
Customer accounts receivable
Billed	113,072	54,514
Unbilled revenues	11,653	8,427
Customers' credit balances and deposits	(22,216)	(32,586)
Customers accounts receivables & Customers' credit balances and deposits	102,509	30,355
Operating Segments | Clean Energy Ventures
Customer accounts receivable
Billed	5,613	5,534
Unbilled revenues	3,379	1,924
Customers' credit balances and deposits	0	0
Customers accounts receivables & Customers' credit balances and deposits	8,992	7,458
Operating Segments | Energy Services
Customer accounts receivable
Billed	141,495	147,087
Unbilled revenues	0	0
Customers' credit balances and deposits	0	0
Customers accounts receivables & Customers' credit balances and deposits	141,495	147,087
Operating Segments | Storage and Transportation
Customer accounts receivable
Billed	5,775	3,956
Unbilled revenues	0	0
Customers' credit balances and deposits	0	0
Customers accounts receivables & Customers' credit balances and deposits	5,775	3,956
Home Services and Other
Customer accounts receivable
Billed	2,088	1,747
Unbilled revenues	0	0
Customers' credit balances and deposits	0	0
Customers accounts receivables & Customers' credit balances and deposits	$ 2,088	$ 1,747