LEASES - Future Minimum Lease Payments under Long-Term Leases (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Operating Leases
2022	$ 11.1
2023	7.6
2024	6.1
2025	3.2
2026	2.5
Thereafter	27.8
Future lease payments	58.3
Less amount representing interest	11.1
Present value of future minimum lease payments	47.2	$ 55.2
Finance Leases
2022	6.0
2023	5.2
2024	5.3
2025	5.2
2026	4.7
Thereafter	56.0
Future lease payments	82.4
Less amount representing interest	23.1
Present value of future minimum lease payments	59.3	62.6
The Connecticut Light and Power Company
Operating Leases
2022	0.1
2023	0.0
2024	0.0
2025	0.0
2026	0.0
Thereafter	0.0
Future lease payments	0.1
Less amount representing interest	0.0
Present value of future minimum lease payments	0.1	0.3
Finance Leases
Present value of future minimum lease payments	0.0	1.4
NSTAR Electric Company
Operating Leases
2022	2.1
2023	2.1
2024	2.1
2025	1.7
2026	1.7
Thereafter	25.3
Future lease payments	35.0
Less amount representing interest	10.7
Present value of future minimum lease payments	24.3	23.6
Finance Leases
2022	0.6
2023	0.7
2024	0.7
2025	0.6
2026	0.6
Thereafter	12.4
Future lease payments	15.6
Less amount representing interest	10.7
Present value of future minimum lease payments	4.9	4.8
Public Service Company of New Hampshire
Operating Leases
2022	0.1
2023	0.1
2024	0.0
2025	0.0
2026	0.0
Thereafter	0.1
Future lease payments	0.3
Less amount representing interest	0.0
Present value of future minimum lease payments	0.3	0.3
Finance Leases
2022	0.1
2023	0.1
2024	0.1
2025	0.1
2026	0.1
Thereafter	0.3
Future lease payments	0.8
Less amount representing interest	0.1
Present value of future minimum lease payments	$ 0.7	$ 0.8