COMMITMENTS, CONTINGENCIES, AND ENVIRONMENTAL MATTERS ENVIRONMENTAL MATTERS (Detail) (USD $)	9 Months Ended
	Sep. 30, 2014
Navajo [Member]
Commitments And Contingencies [Line Items]
Estimated Future Capital Cost For Mercury Emission Control Equipment	$ 1,000,000
Estimated Future Annual Operating Costs for Mercury Emission Control Equipment	1,000,000
Estimated Capital Expenditure for Selective Catalytic Reduction	42,000,000	[1]
Estimated Future Change in Operating Cost for Selective Catalytic Reduction	1,000,000
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	43,000,000
Estimated Future Annual Operating Costs For Mercury Emission Control Equipment and Baghouses	1,000,000
Jointly Owned Utility Plant, Proportionate Ownership Share	7.50%
Four Corner [Member]
Commitments And Contingencies [Line Items]
Estimated Capital Expenditure for Selective Catalytic Reduction	35,000,000	[2]
Estimated Future Change in Operating Cost for Selective Catalytic Reduction	2,000,000
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	5,000,000	[3]
Estimated Future Annual Operating Costs for Mercury Emission Control Equipment	1,000,000	[3]
Percentage of Interest Committed to Purchase	0.495
Third-Party Participating in Ownership Interest	50.50%
TEP's Share (in Percentage) of Obligations for Environmental Costs	100.00%
San Juan [Member]
Commitments And Contingencies [Line Items]
Estimated Capital Expenditure for Selective Non Catalytic Reduction	35,000,000	[4]
Estimated Future Change in Operating Cost for Selective Non Catalytic Reduction	1,000,000
Jointly Owned Utility Plant, Proportionate Ownership Share	50.00%
Jointly Owned Utility Plant, Net Ownership Amount	111,000,000
Sundt [Member]
Commitments And Contingencies [Line Items]
Estimated Capital Expenditure for Monitoring Equipment	1,000,000
Estimated Capital Expenditure for Selective Non Catalytic Reduction	12,000,000	[5]
Jointly Owned Utility Plant, Net Ownership Amount	17,000,000
Sundt [Member] | Minimum [Member]
Commitments And Contingencies [Line Items]
Estimated Future Change in Operating Cost for Selective Non Catalytic Reduction	5,000,000
Sundt [Member] | Maximum [Member]
Commitments And Contingencies [Line Items]
Estimated Future Change in Operating Cost for Selective Non Catalytic Reduction	$ 6,000,000

[1] he EPA published a final rule approving 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. 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 2018. TEP owns 7% of Four Corners Units 4 and 5.

[3] Total capital expenditures and annual O&M expenses represent amounts for both Springerville Units 1 & 2, with estimated costs split equally between the two units. TEP will own 49.5% of Springerville Unit 1 upon close of the lease option purchases in January 2015; after the completion of such purchases, third party owners will be responsible for 50.5% of environmental costs attributable to Springerville Unit 1. TEP will continue to be responsible for 100% of environmental costs attributable to Springerville Unit 2.

[4] In October 2014, the EPA published a final rule approving a state plan covering BART requirements for San Juan, which includes the closure of Units 2 and 3 by December 2017 and the installation of selective non-catalytic reduction (SNCR) on Units 1 and 4 by January 2016. Corresponding to that action, the EPA withdrew the previously applicable FIP addressing the same requirements. Prior to the shutdown of any units in San Juan, PNM must obtain New Mexico Public Regulation Commission approval. If Unit 2 is retired early, TEP expects to request ACC approval to recover all costs associated with the early closure of the unit. TEP owns 50% of San Juan Unit 2. At September 30, 2014, the net book value of TEP's share in San Juan Unit 2 was $111 million.

[5] In June 2014, the EPA issued a final rule 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. TEP is required to notify the EPA of its decision by March 2017. At September 30, 2014, the net book value of the Sundt coal handling facilities was $17 million. If the coal handling facilities are retired early, TEP expects to request ACC approval to recover all the remaining costs of the coal handling facilities.