RELATED PARTY TRANSACTIONS RELATED PARTY TRANSACTIONS (Details) (USD $) In Millions, unless otherwise specified			3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended
	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2014 Tucson Electric Power Company To Uns Electric [Member]	Sep. 30, 2013 Tucson Electric Power Company To Uns Electric [Member]	Sep. 30, 2014 Tucson Electric Power Company To Uns Electric [Member]	Sep. 30, 2013 Tucson Electric Power Company To Uns Electric [Member]	Sep. 30, 2014 Uns Electric To Tucson Electric Power Company [Member]	Sep. 30, 2013 Uns Electric To Tucson Electric Power Company [Member]	Sep. 30, 2014 Uns Electric To Tucson Electric Power Company [Member]	Sep. 30, 2013 Uns Electric To Tucson Electric Power Company [Member]	Sep. 30, 2014 TEP to UNS Energy Affiliates [Member]	Sep. 30, 2013 TEP to UNS Energy Affiliates [Member]	Sep. 30, 2014 TEP to UNS Energy Affiliates [Member]	Sep. 30, 2013 TEP to UNS Energy Affiliates [Member]	Sep. 30, 2014 Southwest Energy Solutions, Inc. to TEP [Member]	Sep. 30, 2013 Southwest Energy Solutions, Inc. to TEP [Member]	Sep. 30, 2014 Southwest Energy Solutions, Inc. to TEP [Member]	Sep. 30, 2013 Southwest Energy Solutions, Inc. to TEP [Member]	Sep. 30, 2014 UNS Energy Affiliates to TEP [Member]	Sep. 30, 2013 UNS Energy Affiliates to TEP [Member]	Sep. 30, 2014 UNS Energy Affiliates to TEP [Member]	Sep. 30, 2013 UNS Energy Affiliates to TEP [Member]	Sep. 30, 2014 UNS Electric [Member]	Dec. 31, 2013 UNS Electric [Member]	Sep. 30, 2014 Uns Gas [Member]	Dec. 31, 2013 Uns Gas [Member]	Sep. 30, 2014 Uns Energy Corporation [Member]	Dec. 31, 2013 Uns Energy Corporation [Member]	Sep. 30, 2014 Southwest Energy Solutions, Inc. [Member]	Dec. 31, 2013 Southwest Energy Solutions, Inc. [Member]
Related Party Transaction [Line Items]
Wholesale Sales from Related Parties			$ 2	$ 0	$ 3	$ 1
Wholesale Purchases from Related Parties							2	0	3	1
Control Area Services, Other Revenues from Transactions with Related Parties			1	1	2	3
Common Costs Charged to Related Parties											3	3	10	9
Supplemental Workforce, Maintenance Costs															4	4	12	11
Corporate Services and Other Labor Charges											3	4	7	10					0	0	1	1
Related Party Transaction, Due from (to) Related Parties [Abstract]
Receivable from Related Parties	3	6																					2	3	1	2	0	1
Payable to Related Parties	$ 4	$ 9																					$ 1	$ 0			$ 0	$ 7	$ 3	$ 2