REVENUE - TIMING OF REVENUE RECOGNITION - BALANCE SHEET (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Sep. 30, 2021	Mar. 31, 2021	Sep. 30, 2020
Customer accounts receivable
Billed	$ 273,313	$ 212,838	$ 237,229	$ 134,173
Unbilled revenues	56,270	10,351	41,941	9,226
Customers' credit balances and deposits	(20,284)	(32,586)	$ (20,763)	$ (25,934)
Customers accounts receivables & Customers' credit balances and deposits	309,299	190,603
Operating Segments | Natural Gas Distribution
Customer accounts receivable
Billed	154,380	54,514
Unbilled revenues	54,675	8,427
Customers' credit balances and deposits	(20,284)	(32,586)
Customers accounts receivables & Customers' credit balances and deposits	188,771	30,355
Operating Segments | Clean Energy Ventures
Customer accounts receivable
Billed	5,239	5,534
Unbilled revenues	1,595	1,924
Customers' credit balances and deposits	0	0
Customers accounts receivables & Customers' credit balances and deposits	6,834	7,458
Operating Segments | Energy Services
Customer accounts receivable
Billed	107,262	147,087
Unbilled revenues	0	0
Customers' credit balances and deposits	0	0
Customers accounts receivables & Customers' credit balances and deposits	107,262	147,087
Operating Segments | Storage and Transportation
Customer accounts receivable
Billed	4,385	3,956
Unbilled revenues	0	0
Customers' credit balances and deposits	0	0
Customers accounts receivables & Customers' credit balances and deposits	4,385	3,956
Home Services and Other
Customer accounts receivable
Billed	2,047	1,747
Unbilled revenues	0	0
Customers' credit balances and deposits	0	0
Customers accounts receivables & Customers' credit balances and deposits	$ 2,047	$ 1,747