RELATED PARTY TRANSACTIONS (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Related Party Transaction, Due from (to) Related Parties [Abstract]
Receivables from Related Parties	$ 26	$ 17
Payables to Related Parties	7	2
Transmission Revenues, UNS Electric
Related Party Transaction, Due from (to) Related Parties [Abstract]
Transmission and wholesale revenue	5	11	$ 9
Wholesale Revenues, UNS Electric
Related Party Transaction, Due from (to) Related Parties [Abstract]
Transmission and wholesale revenue	50	25	1
Control Area Services, UNS Electric
Related Party Transaction, Due from (to) Related Parties [Abstract]
Control area services and corporate services	3	6	4
Common Costs, UNS Energy Affiliates
Related Party Transaction, Due from (to) Related Parties [Abstract]
Common costs, UNS energy affiliates	22	21	19
Wholesale Revenues, UNS Electric
Related Party Transaction, Due from (to) Related Parties [Abstract]
Revenue expenses	2	1	0
Supplemental Workforce, SES
Related Party Transaction, Due from (to) Related Parties [Abstract]
Supplemental workforce, SES	0	0	14
Corporate Services, UNS Energy
Related Party Transaction, Due from (to) Related Parties [Abstract]
Corporate services	$ 8	7	5
Intercompany allocation parent to subsidiary (in percentage)	85.00%
Management fee	$ 7	6	6
Corporate Services, UNS Energy Affiliates
Related Party Transaction, Due from (to) Related Parties [Abstract]
Corporate services	1	3	4
Capacity Charges, UNS Gas
Related Party Transaction, Due from (to) Related Parties [Abstract]
Capacity charges, UNS gas	1	0	0
Corporate Services, Fortis Affiliates
Related Party Transaction, Due from (to) Related Parties [Abstract]
Corporate services	0	0	$ 1
UNS Electric
Related Party Transaction, Due from (to) Related Parties [Abstract]
Receivables from Related Parties	22	8
Payables to Related Parties	5	0
UNS Energy
Related Party Transaction, Due from (to) Related Parties [Abstract]
Receivables from Related Parties	2	7
Payables to Related Parties	1	1
UNS Gas
Related Party Transaction, Due from (to) Related Parties [Abstract]
Receivables from Related Parties	2	2
Payables to Related Parties	$ 1	$ 1

Common Costs Charged to Related Parties - Common Cost Allocations

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Intercompany Allocation Parent to Subsidiary

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Management Fee

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Related Party Transaction, Capacity Charges

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The aggregate costs related to goods produced and sold and services rendered by an entity during the reporting period. This excludes costs incurred during the reporting period related to financial services rendered and other revenue generating activities.

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Expenses recognized resulting from transactions (excluding transactions that are eliminated in consolidated or combined financial statements) with related party.

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Amount of selling, general and administrative expenses resulting from transactions, excluding transactions that are eliminated in consolidated or combined financial statements, with related party.

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Amount of revenue, fees and commissions earned from transactions between (a) a parent company and its subsidiaries; (b) subsidiaries of a common parent; (c) an entity and trusts for the benefit of employees, for example, but not limited to, pension and profit-sharing trusts that are managed by or under the trusteeship of the entity's management; (d) an entity and its principal, owners, management, or members of their immediate families; and (e) affiliates.

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