RELATED PARTY TRANSACTIONS (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024	Dec. 31, 2024
Related Party Transaction [Line Items]
Accounts Payable	$ 207,753		$ 207,753		$ 151,278
Operating Revenues	407,244	$ 429,546	772,980	$ 882,302
Other	7,000	7,000	35,000	41,000
Related Party
Related Party Transaction [Line Items]
Accounts Receivable, Net	9,000		9,000		10,000
Accounts Payable	3,000		3,000		2,000
Related Party | Common Costs, UNS Energy Affiliates
Related Party Transaction [Line Items]
Common costs	6,000	6,000	12,000	12,000
Related Party | Transmission Revenues, UNS Electric
Related Party Transaction [Line Items]
Operating Revenues	2,000	2,000	4,000	4,000
Related Party | Wholesale Revenues, UNS Electric
Related Party Transaction [Line Items]
Operating Revenues	0	1,000	1,000	3,000
Related Party | Control Area Services, UNS Electric
Related Party Transaction [Line Items]
Other	1,000	1,000	1,000	1,000
Related Party | Corporate Services, UNS Energy
Related Party Transaction [Line Items]
Corporate services	3,000	2,000	$ 6,000	5,000
Massachusetts formula - TEP's allocation (percentage)			84.00%
Management fee	2,000	2,000	$ 5,000	4,000
Related Party | Purchased Power, UNS Electric
Related Party Transaction [Line Items]
Purchased power	0	0	1,000	0
Related Party | Capacity Charges , UNS Gas
Related Party Transaction [Line Items]
Capacity charges	0	0	1,000	1,000
Related Party | Corporate Services, UNS Energy Affiliates
Related Party Transaction [Line Items]
Corporate services	1,000	$ 1,000	1,000	$ 1,000
Related Party | UNS Electric
Related Party Transaction [Line Items]
Accounts Receivable, Net	7,000		7,000		7,000
Accounts Payable	1,000		1,000		1,000
Related Party | UNS Gas
Related Party Transaction [Line Items]
Accounts Receivable, Net	2,000		2,000		2,000
Related Party | UNS Energy
Related Party Transaction [Line Items]
Accounts Receivable, Net	0		0		1,000
Accounts Payable	$ 2,000		$ 2,000		$ 1,000