LEASES - FUTURE MINIMUM LEASE PAYMENTS (Details) $ in Millions	Dec. 31, 2019 USD ($)
Finance leases
2020	$ 0.6
2021	1.0
2022	1.0
2023	1.0
2024	1.0
Thereafter	85.4
Total minimum lease payments	90.0
Less: interest	(59.3)
Present value of minimum lease payments	30.7
Less: short-term lease liabilities	0.0
Long-term lease liabilities	30.7
Two Creeks Solar Project
Finance leases
2020	0.3
2021	0.3
2022	0.3
2023	0.3
2024	0.3
Thereafter	32.0
Total minimum lease payments	33.5
Less: interest	(22.6)
Present value of minimum lease payments	10.9
Less: short-term lease liabilities	0.0
Long-term lease liabilities	10.9
Badger Hollow Solar Farm I
Finance leases
2020	0.3
2021	0.7
2022	0.7
2023	0.7
2024	0.7
Thereafter	53.4
Total minimum lease payments	56.5
Less: interest	(36.7)
Present value of minimum lease payments	19.8
Less: short-term lease liabilities	0.0
Long-term lease liabilities	$ 19.8