REVENUE - TIMING OF REVENUE RECOGNITION - BALANCE SHEET (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Sep. 30, 2019
Customer accounts receivable
Billed	$ 250,419	$ 139,263
Unbilled revenues	63,656	6,510
Customers' credit	(29,573)	$ (27,116)
Customers accounts receivables & Customers' credit balances and deposits	284,502
Operating Segments | Natural Gas Distribution
Customer accounts receivable
Billed	78,365
Unbilled revenues	63,656
Customers' credit	(29,573)
Customers accounts receivables & Customers' credit balances and deposits	112,448
Operating Segments | Clean Energy Ventures
Customer accounts receivable
Billed	3,059
Unbilled revenues	0
Customers' credit	0
Customers accounts receivables & Customers' credit balances and deposits	3,059
Operating Segments | Energy Services
Customer accounts receivable
Billed	164,688
Unbilled revenues	0
Customers' credit	0
Customers accounts receivables & Customers' credit balances and deposits	164,688
Operating Segments | Midstream
Customer accounts receivable
Billed	2,727
Unbilled revenues	0
Customers' credit	0
Customers accounts receivables & Customers' credit balances and deposits	2,727
Home Services and Other
Customer accounts receivable
Billed	2,355
Unbilled revenues	0
Customers' credit	0
Customers accounts receivables & Customers' credit balances and deposits	2,355
Eliminations
Customer accounts receivable
Billed	(775)
Unbilled revenues	0
Customers' credit	0
Customers accounts receivables & Customers' credit balances and deposits	$ (775)