RELATED PARTY TRANSACTIONS (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Related Party Transaction [Line Items]
Accounts Receivable	$ 217,381	$ 320,899
Accounts Payable	137,002	233,920
Operating Revenues	1,875,448	1,808,082	$ 1,592,586
Other	66,000	80,000	101,000
Related Party
Related Party Transaction [Line Items]
Accounts Receivable	7,000	26,000
Accounts Payable	3,000	7,000
Related Party \| Transmission Revenues, UNS Electric
Related Party Transaction [Line Items]
Operating Revenues	8,000	5,000	11,000
Related Party \| Wholesale Revenues, UNS Electric
Related Party Transaction [Line Items]
Operating Revenues	39,000	50,000	25,000
Related Party \| Control Area Services, UNS Electric
Related Party Transaction [Line Items]
Other	2,000	3,000	6,000
Related Party \| Common Costs, UNS Energy Affiliates
Related Party Transaction [Line Items]
Common Costs Charged	23,000	22,000	21,000
Related Party \| Purchased Power, UNS Electric
Related Party Transaction [Line Items]
Purchased Power, UNS Electric	2,000	2,000	1,000
Related Party \| Corporate Services, UNS Energy
Related Party Transaction [Line Items]
Corporate Services	$ 8,000	8,000	7,000
Massachusetts formula - TEP's allocation (percentage)	85.00%
Management fee	$ 7,000	7,000	6,000
Related Party \| Corporate Services, UNS Energy Affiliates
Related Party Transaction [Line Items]
Corporate Services	1,000	1,000	3,000
Related Party \| Capacity Charges, UNS Gas
Related Party Transaction [Line Items]
Capacity Charges, UNS Gas	2,000	1,000	$ 0
UNS Electric \| Related Party
Related Party Transaction [Line Items]
Accounts Receivable	5,000	22,000
Accounts Payable	1,000	5,000
UNS Gas \| Related Party
Related Party Transaction [Line Items]
Accounts Receivable	2,000	2,000
Accounts Payable	1,000	1,000
UNS Energy \| Related Party
Related Party Transaction [Line Items]
Accounts Receivable	0	2,000
Accounts Payable	$ 1,000	$ 1,000

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