COMMITMENTS, CONTINGENCIES, AND ENVIRONMENTAL MATTERS (Environmental Matters) (Detail) (TUCSON ELECTRIC POWER COMPANY, USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014
Navajo [Member]
Commitments And Contingencies [Line Items]
Estimated Future Capital Cost For Mercury Emission Control Equipment	$ 1
Estimated Future Annual Operating Costs for Mercury Emission Control Equipment	1
Estimated Capital Expenditure for Selective Catalytic Reduction	42	[1]
Estimated Future Change in Operating Cost for Selective Catalytic Reduction	1	[1]
Better Than BART Agreement Year by which to Shut Down One Unit	2020
Better than BART Agreement, Year by which SCR Technology to be Installed	2030
Better than BART Agreement, Year by which Coal Fired Operation will Cease	2044
Estimated Capital Expenditure Related to Installation of Baghouses	43
Estimated Future Annual Operating Costs For Mercury Emission Control Equipment and Baghouses	1
Jointly Owned Utility Plant, Proportionate Ownership Share	7.50%
Four Corner [Member]
Commitments And Contingencies [Line Items]
Estimated Future Capital Cost For Mercury Emission Control Equipment	1
Estimated Future Annual Operating Costs for Mercury Emission Control Equipment	1
Estimated Capital Expenditure for Selective Catalytic Reduction	35	[2]
Estimated Future Change in Operating Cost for Selective Catalytic Reduction	2	[2]
Jointly Owned Utility Plant, Proportionate Ownership Share	7.00%
Springerville [Member]
Commitments And Contingencies [Line Items]
Estimated Future Capital Cost For Mercury Emission Control Equipment	5
Estimated Future Annual Operating Costs for Mercury Emission Control Equipment	3
San Juan [Member]
Commitments And Contingencies [Line Items]
Estimated Capital Expenditure for Selective Non Catalytic Reduction	35	[3]
Estimated Future Change in Operating Cost for Selective Catalytic Reduction	6
Estimated Future Change in Operating Cost for Selective Non Catalytic Reduction	1	[3]
Jointly Owned Utility Plant, Proportionate Ownership Share	50.00%
Jointly Owned Utility Plant, Net Ownership Amount	112
San Juan [Member] | Minimum [Member]
Commitments And Contingencies [Line Items]
Estimated Capital Expenditure for Selective Catalytic Reduction	180
San Juan [Member] | Maximum [Member]
Commitments And Contingencies [Line Items]
Estimated Capital Expenditure for Selective Catalytic Reduction	200
Sundt [Member]
Commitments And Contingencies [Line Items]
Estimated Capital Expenditure for Selective Non Catalytic Reduction	12
Jointly Owned Utility Plant, Net Ownership Amount	27
Sundt [Member] | Minimum [Member]
Commitments And Contingencies [Line Items]
Estimated Future Change in Operating Cost for Selective Non Catalytic Reduction	5	[4]
Sundt [Member] | Maximum [Member]
Commitments And Contingencies [Line Items]
Estimated Future Change in Operating Cost for Selective Non Catalytic Reduction	$ 6	[4]

[1] The EPA is considering a better-than-BART plan wherein: one unit at Navajo will be shut down by 2020; SCR (or the equivalent) will be installed on the remaining two units by 2030; and conventional coal-fired generation will cease by December 2044. TEP expects the EPA to reach a decision in 2014. In addition, the installation of SCR technology could increase particulates which may require that baghouses be installed. TEP owns 7.5% of Navajo. TEP's share of the capital cost of baghouses in addition to the SCR costs reflected in the table above is approximately $43 million with O&M on the baghouses expected to be less than $1 million per year.

[2] In December 2013, APS, on behalf of the co-owners of Four Corners, notified the EPA that they have chosen an alternative BART compliance strategy; as a result, APS closed Units 1, 2, and 3 in December 2013 and has agreed to the installation of SCR on Units 4 & 5 by July 31, 2018. TEP owns 7% of Four Corners Units 4 and 5.

[3] The Federal Implementation Plan (FIP) for San Juan requires SCRs for which TEP estimates its share of capital costs will be $180-$200 million with annual O&M of $6 million. As part of a proposal for an alternative, Public Service Company of New Mexico (PNM), the State of New Mexico, and the EPA signed a non-binding agreement in which PNM agreed to close Units 2 and 3 by December 31, 2017 and install selective non-catalytic reduction (SNCR) on Units 1 and 4 by January 2016 or later depending on the timing of EPA approvals. These estimated costs are reflected in the table above. The State of New Mexico has submitted this plan to the EPA for approval. TEP expects the EPA will reach a decision in 2014. TEP owns 50% of San Juan Unit 2. At March 31, 2014, the net book value of TEP's share in San Juan Unit 2 was $112 million. If Unit 2 is retired early, TEP expects to request ACC approval to recover, over a reasonable time period, all costs associated with the early closure of the unit.

[4] In January 2014, the EPA issued a proposal that would require TEP to either (i) install SNCR and dry sorbent injection technology on Unit 4 by mid-2017 or (ii) eliminate the use of coal by the end of 2017 as a better-than-BART alternative. Under the proposal, TEP would be required to notify the EPA of its decision by July 31, 2015. The EPA is expected to issue a final BART determination by July 2014. At March 31, 2014, the net book value of the Sundt coal handling facilities was $27 million. If the coal handling facilities are retired early, TEP expects to request ACC approval to recover, over a reasonable time period, all the remaining costs of the coal handling facilities.