REVENUE - TIMING OF REVENUE RECOGNITION - BALANCE SHEET (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Sep. 30, 2019
Customer accounts receivable
Billed	$ 143,059	$ 139,263
Unbilled revenues	8,738	6,510
Customers' credit balances and deposits	(20,056)	$ (27,116)
Customers accounts receivables & Customers' credit balances and deposits	131,741
Operating Segments | Natural Gas Distribution
Customer accounts receivable
Billed	78,370
Unbilled revenues	8,738
Customers' credit balances and deposits	(20,056)
Customers accounts receivables & Customers' credit balances and deposits	67,052
Operating Segments | Clean Energy Ventures
Customer accounts receivable
Billed	3,469
Unbilled revenues	0
Customers' credit balances and deposits	0
Customers accounts receivables & Customers' credit balances and deposits	3,469
Operating Segments | Energy Services
Customer accounts receivable
Billed	55,364
Unbilled revenues	0
Customers' credit balances and deposits	0
Customers accounts receivables & Customers' credit balances and deposits	55,364
Operating Segments | Midstream
Customer accounts receivable
Billed	3,828
Unbilled revenues	0
Customers' credit balances and deposits	0
Customers accounts receivables & Customers' credit balances and deposits	3,828
Home Services and Other
Customer accounts receivable
Billed	2,028
Unbilled revenues	0
Customers' credit balances and deposits	0
Customers accounts receivables & Customers' credit balances and deposits	$ 2,028