SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - ADDITIONAL INFORMATION (Details) - USD ($)	1 Months Ended		6 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Mar. 31, 2021	Mar. 31, 2020	Sep. 30, 2020
Finite-Lived Intangible Assets [Line Items]
Reserve for expected credit losses			$ 10,607,000	$ 951,000
Loans receivable in other current assets			14,300,000		$ 13,700,000
Loans receivable in other noncurrent assets			33,900,000		$ 35,300,000
Proceeds from sale leaseback transaction			0	4,000,000
Proceeds from sale leaseback transaction - solar	$ 12,100,000		12,124,000	$ 0
Clean Energy Ventures
Finite-Lived Intangible Assets [Line Items]
Reserve for expected credit losses			5,200,000
Natural Gas Distribution
Finite-Lived Intangible Assets [Line Items]
Proceeds from sale leaseback transaction		$ 4,000,000.0	$ 0
Minimum
Finite-Lived Intangible Assets [Line Items]
Loans receivable, term			2 years
Maximum
Finite-Lived Intangible Assets [Line Items]
Loans receivable, term			10 years