LEASES - ADDITIONAL INFORMATION (Details) $ in Millions	3 Months Ended	6 Months Ended
	Mar. 31, 2020 USD ($) extension lease	Mar. 31, 2020 USD ($) extension lease
Lessee, Lease, Description [Line Items]
ROU asset obtained in exchange for operating lease liability	$ 12.4	$ 45.7
ROU asset obtained in exchange for finance lease liability	$ 34.0	$ 49.7
Weighted average remaining lease term, operating lease	27 years 4 months 24 days	27 years 4 months 24 days
Weighted average remaining lease term, finance lease	2 years 7 months 17 days	2 years 7 months 17 days
Operating lease, discount rate	3.18%	3.18%
Finance lease, discount rate	2.56%	2.56%
Number of leases not yet commenced | lease	3	3
Lease not yet commenced, estimated payments	$ 5.7	$ 5.7
Number of options to extend | extension	2	2
Renewal term	5 years	5 years
Solar Property | Minimum
Lessee, Lease, Description [Line Items]
Term of contract	15 years	15 years
Renewal term	5 years	5 years
Solar Property | Maximum
Lessee, Lease, Description [Line Items]
Term of contract	25 years	25 years
Renewal term	10 years	10 years
Office Building | Minimum
Lessee, Lease, Description [Line Items]
Term of contract	1 year	1 year
Office Building | Maximum
Lessee, Lease, Description [Line Items]
Term of contract	25 years	25 years
Meter License
Lessee, Lease, Description [Line Items]
Term of contract	7 years	7 years
Equipment
Lessee, Lease, Description [Line Items]
Term of contract	5 years	5 years
Storage and Capacity
Lessee, Lease, Description [Line Items]
Term of contract	50 years	50 years