LEASES - Future Minimum Lease Payments under Long-Term Leases (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Operating Leases
2023	$ 10.3
2024	9.3
2025	6.4
2026	5.5
2027	5.2
Thereafter	31.2
Future lease payments	67.9
Less amount representing interest	11.0
Present value of future minimum lease payments	56.9	$ 47.2
Finance Leases
2023	5.9
2024	5.9
2025	5.9
2026	5.4
2027	5.4
Thereafter	50.9
Future lease payments	79.4
Less amount representing interest	21.4
Present value of future minimum lease payments	58.0	59.3
CL&P
Operating Leases
2023	0.7
2024	0.7
2025	0.7
2026	0.3
2027	0.0
Thereafter	0.0
Future lease payments	2.4
Less amount representing interest	0.2
Present value of future minimum lease payments	2.2	0.1
Finance Leases
Present value of future minimum lease payments	0.0	0.0
NSTAR Electric
Operating Leases
2023	2.1
2024	2.1
2025	1.7
2026	1.7
2027	1.7
Thereafter	23.6
Future lease payments	32.9
Less amount representing interest	10.4
Present value of future minimum lease payments	22.5	24.3
Finance Leases
2023	0.6
2024	0.6
2025	0.6
2026	0.7
2027	0.7
Thereafter	11.8
Future lease payments	15.0
Less amount representing interest	10.1
Present value of future minimum lease payments	$ 4.9	$ 4.9