Regulation	3 Months Ended
Mar. 31, 2015
Public Utilities, General Disclosures [Abstract]
Regulation	Regulation General The rates and services of the Company are regulated by incorporated municipalities in Texas, the Public Utility Commission of Texas ("PUCT"), the New Mexico Public Regulation Commission ("NMPRC"), and the Federal Energy Regulatory Commission ("FERC"). Municipal orders, ordinances and other agreements regarding rates and services adopted by Texas municipalities are subject to review and approval by the PUCT. The FERC has jurisdiction over the Company's wholesale (sales for resale) transactions, transmission service and compliance with federally-mandated reliability standards. The decisions of the PUCT, the NMPRC and the FERC are subject to judicial review. Texas Regulatory Matters 2012 Texas Retail Rate Case. On April 17, 2012, the El Paso City Council approved the settlement of the Company's 2012 Texas retail rate case and fuel reconciliation in PUCT Docket No. 40094. The PUCT issued a final order approving the settlement on May 23, 2012 and the rates were effective as of May 1, 2012. As part of the 2012 Texas retail rate settlement, the Company agreed to submit a future fuel reconciliation request covering the period beginning July 1, 2009 and ending no later than June 30, 2013 by December 31, 2013 or as part of its next rate case, if earlier. The Company filed a fuel reconciliation request covering the period July 1, 2009 through March 31, 2013, as discussed below. The 2012 Texas retail rate settlement also provided for the continuation of the energy efficiency cost recovery factor and the military base discount recovery factor. Both of these surcharges require annual filings to reconcile and revise the recovery factors. Energy Efficiency Cost Recovery Factor. The Company made its annual filing to establish its energy efficiency cost recovery factor for 2015 on May 1, 2014. In addition to projected energy efficiency costs for 2015 and true-up to prior year actual costs, the Company requested approval of a $2.0 million bonus for the 2013 energy efficiency program results in accordance with PUCT rules. The PUCT approved the Company's request at its November 14, 2014 open meeting. The Company recorded the $2.0 million bonus as operating revenue in the fourth quarter of 2014. On May 1, 2015, the Company made its annual filing to establish its energy efficiency cost recovery factor for 2016. In addition to projected energy efficiency costs for 2016 and true-up to prior year actual costs, the Company requested approval of a $1.0 million bonus for the 2014 energy efficiency program results in accordance with PUCT rules. This case was assigned PUCT Docket No. 44677. No procedural schedule has yet been issued. Fuel and Purchased Power Costs. The Company's actual fuel costs, including purchased power energy costs, are recovered from customers through a fixed fuel factor. The PUCT has adopted a fuel cost recovery rule (the "Texas Fuel Rule") that allows the Company to seek periodic adjustments to its fixed fuel factor. The Company can seek to revise its fixed fuel factor based upon the approved formula at least four months after its last revision except in the month of December. The Texas Fuel Rule requires the Company to request to refund fuel costs in any month when the over-recovery balance exceeds a threshold material amount and it expects fuel costs to continue to be materially over-recovered. The Texas Fuel Rule also permits the Company to seek to surcharge fuel under-recoveries in any month the balance exceeds a threshold material amount and it expects fuel cost recovery to continue to be materially under-recovered. Fuel over and under-recoveries are considered material when they exceed 4% of the previous twelve months' fuel costs. All such fuel revenue and expense activities are subject to periodic final review by the PUCT in fuel reconciliation proceedings. On April 15, 2014, the Company filed a request, which was assigned PUCT Docket No. 42384, to increase its fixed fuel factor by approximately $10.7 million annually or 6.9%, pursuant to its approved formula. The revised fixed fuel factor reflected an expected increase in prices for natural gas over the twelve month period beginning March 2014. The increase in the fixed fuel factor received final approval on May 28, 2014 and was effective with May 2014 billings. As of March 31, 2015, the Company had slightly over-recovered fuel costs in the amount of $3.6 million for the Texas jurisdiction. On April 15, 2015, the Company filed a request, which was assigned PUCT Docket No. 44633, to reduce its fixed fuel factor by approximately 24% to reflect the reduction in fuel expense. The over-recovered balance is below the materiality threshold. On April 30, 2015, the Administrative Law Judge issued an order approving the proposed reduction on an interim basis effective May 1, 2015. Fuel Reconciliation Proceeding. Pursuant to the 2012 Texas retail rate settlement discussed above, on September 27, 2013, the Company filed an application with the PUCT, designated as PUCT Docket No. 41852, to reconcile $545.3 million of fuel and purchased power expenses incurred during the 45-month period from July 1, 2009 through March 31, 2013. A settlement was reached and a final order was issued by the PUCT on July 11, 2014. The PUCT's final order completes the regulatory review and reconciliation of the Company's fuel expenses for the period through March 31, 2013. The settlement provides that 100% of margins on non-arbitrage off-system sales (as defined by the settlement) and 50% of margins on arbitrage off-system sales be shared with its Texas customers beginning April 1, 2014. For the period April 1, 2014 through June 30, 2015, the Company's total share of margins assignable to Texas retail jurisdiction, on arbitrage and non-arbitrage off-system sales, may not exceed 10% of the total margins assignable to the Texas retail jurisdiction on all off-system sales. The Company also agreed to file with the PUCT a proceeding to address the reasonableness of the Company's decision to not continue to participate in the Four Corners coal-fired generating Units 4 and 5 after July 2016. It is expected that issues related to the final coal mine closing and reclamation costs will be addressed in that proceeding as well as other issues related to post-participation events such as the asset retirement obligations of the Company related to those two units. Montana Power Station Approvals. The Company has received a Certificate of Convenience and Necessity ("CCN") from the PUCT to construct four natural gas fired generating units at the Montana Power Station ("the MPS") in El Paso County, Texas. The Company also obtained air permits from the Texas Commission on Environmental Quality ("TCEQ") and the U.S. Environmental Protection Agency ("EPA"). The PUCT has issued final orders approving CCNs for the MPS to Caliente transmission line, MPS In & Out transmission line and the MPS to Montwood transmission line. These transmission lines will connect MPS to the Company’s transmission system for delivery of electricity throughout its service territory. MPS Units 1 and 2 and the MPS to Caliente and MPS In & Out transmission lines became operational in March 2015. Solar Generation CCN Filing. On April 20, 2015, the Company filed a petition with the PUCT requesting CCN authorization to construct a new 20 megawatt solar-powered generation facility to be located on Fort Bliss in the Company's service territory in Texas. The new facility will be a system resource. The Company has requested a PUCT final order by November 30, 2015 so that the project can be completed before December 31, 2016 to maximize potential tax benefits. This case was assigned PUCT Docket No. 44637. No procedural schedule has yet been issued. Other Required Approvals. The Company has obtained other required approvals for recovery of fuel costs through fixed fuel factors, other tariffs and approvals as required by the Public Utility Regulatory Act (the "PURA") and the PUCT. New Mexico Regulatory Matters 2009 New Mexico Stipulation. On December 10, 2009, the NMPRC issued a final order conditionally approving the stipulated rates in NMPRC Case No. 09-00171-UT. The stipulated rates went into effect with January 2010 bills. The stipulated rates provide for an Efficient Use of Energy Factor Rate Rider to recover energy efficiency expenditures which are updated annually for adjustment to the recovery factors. Fuel and Purchased Power Costs. Fuel and purchased power costs are recovered through base rates and a Fuel and Purchased Power Cost Adjustment Clause (the "FPPCAC") that accounts for changes in the costs of fuel included in base rates. On January 8, 2014, the NMPRC approved the continuation of the FPPCAC without modification in NMPRC Case No. 13-00380-UT. Fuel and purchased power costs are reconciled to actual costs on a monthly basis and recovered or refunded to customers the second succeeding month. The Company recovers costs related to Palo Verde Unit 3 capacity and energy in New Mexico through the FPPCAC as purchased power using a proxy market price approved in the 2014 FPPCAC continuation. Montana Power Station Approvals. The Company has received a CCN from the NMPRC to construct four units at the MPS and associated transmission lines. The Company also obtained all necessary air permits from the TCEQ and EPA. A final order in NMPRC Case No. 13-00297-UT approving the CCN for MPS Units 3 and 4 was issued on June 11, 2014. MPS Units 1 and 2 and the MPS to Caliente and MPS In & Out transmission lines became operational in March 2015. Solar Generation CCN Filing. On April 20, 2015, the Company filed a petition with the NMPRC requesting CCN authorization to construct a new 20 megawatt solar-powered generation facility to be located on Fort Bliss in the Company's service territory in Texas. The new facility will be a system resource. The Company has requested a NMPRC final order by November 30, 2015 so that the project can be completed before December 31, 2016 to maximize potential tax benefits. This case was assigned NMPRC Case No. 15-00099-UT. No procedural schedule has yet been issued. Other Required Approvals. The Company has obtained other required approvals for other tariffs, securities transactions, long-term resource plans, recovery of energy efficiency costs through a base rate rider and other approvals as required by the NMPRC. Federal Regulatory Matters Public Service Company of New Mexico's ("PNM") Transmission Rate Case. On December 31, 2012, PNM filed with FERC to change its method of transmission rate recovery for its transmission delivery services from stated rates to formula rates. The Company takes transmission service from PNM and is among the PNM transmission customers affected by PNM's shift to formula rates. On March 1, 2013, the FERC issued an order rejecting in part PNM's filing, and establishing settlement judge and hearing procedures. On March 20, 2015, PNM filed with FERC a settlement agreement and offer of settlement resolving all issues set for hearing in the proceeding. The Company cannot predict the outcome of the case at this time. Other Required Approvals. The Company has obtained required approvals for rates and tariffs, securities transactions and other approvals as required by the FERC.

Regulation

General

The rates and services of the Company are regulated by incorporated municipalities in Texas, the Public Utility Commission of Texas ("PUCT"), the New Mexico Public Regulation Commission ("NMPRC"), and the Federal Energy Regulatory Commission ("FERC"). Municipal orders, ordinances and other agreements regarding rates and services adopted by Texas municipalities are subject to review and approval by the PUCT. The FERC has jurisdiction over the Company's wholesale (sales for resale) transactions, transmission service and compliance with federally-mandated reliability standards. The decisions of the PUCT, the NMPRC and the FERC are subject to judicial review.

Texas Regulatory Matters

2012 Texas Retail Rate Case. On April 17, 2012, the El Paso City Council approved the settlement of the Company's 2012 Texas retail rate case and fuel reconciliation in PUCT Docket No. 40094. The PUCT issued a final order approving the settlement on May 23, 2012 and the rates were effective as of May 1, 2012. As part of the 2012 Texas retail rate settlement, the Company agreed to submit a future fuel reconciliation request covering the period beginning July 1, 2009 and ending no later than June 30, 2013 by December 31, 2013 or as part of its next rate case, if earlier. The Company filed a fuel reconciliation request covering the period July 1, 2009 through March 31, 2013, as discussed below. The 2012 Texas retail rate settlement also provided for the continuation of the energy efficiency cost recovery factor and the military base discount recovery factor. Both of these surcharges require annual filings to reconcile and revise the recovery factors.

Energy Efficiency Cost Recovery Factor. The Company made its annual filing to establish its energy efficiency cost recovery factor for 2015 on May 1, 2014. In addition to projected energy efficiency costs for 2015 and true-up to prior year actual costs, the Company requested approval of a $2.0 million bonus for the 2013 energy efficiency program results in accordance with PUCT rules. The PUCT approved the Company's request at its November 14, 2014 open meeting. The Company recorded the $2.0 million bonus as operating revenue in the fourth quarter of 2014.

On May 1, 2015, the Company made its annual filing to establish its energy efficiency cost recovery factor for 2016. In addition to projected energy efficiency costs for 2016 and true-up to prior year actual costs, the Company requested approval of a $1.0 million bonus for the 2014 energy efficiency program results in accordance with PUCT rules. This case was assigned PUCT Docket No. 44677. No procedural schedule has yet been issued.

Fuel and Purchased Power Costs. The Company's actual fuel costs, including purchased power energy costs, are recovered from customers through a fixed fuel factor. The PUCT has adopted a fuel cost recovery rule (the "Texas Fuel Rule") that allows the Company to seek periodic adjustments to its fixed fuel factor. The Company can seek to revise its fixed fuel factor based upon the approved formula at least four months after its last revision except in the month of December. The Texas Fuel Rule requires the Company to request to refund fuel costs in any month when the over-recovery balance exceeds a threshold material amount and it expects fuel costs to continue to be materially over-recovered. The Texas Fuel Rule also permits the Company to seek to surcharge fuel under-recoveries in any month the balance exceeds a threshold material amount and it expects fuel cost recovery to continue to be materially under-recovered. Fuel over and under-recoveries are considered material when they exceed 4% of the previous twelve months' fuel costs. All such fuel revenue and expense activities are subject to periodic final review by the PUCT in fuel reconciliation proceedings.

On April 15, 2014, the Company filed a request, which was assigned PUCT Docket No. 42384, to increase its fixed fuel factor by approximately $10.7 million annually or 6.9%, pursuant to its approved formula. The revised fixed fuel factor reflected an expected increase in prices for natural gas over the twelve month period beginning March 2014. The increase in the fixed fuel factor received final approval on May 28, 2014 and was effective with May 2014 billings. As of March 31, 2015, the Company had slightly over-recovered fuel costs in the amount of $3.6 million for the Texas jurisdiction. On April 15, 2015, the Company filed a request, which was assigned PUCT Docket No. 44633, to reduce its fixed fuel factor by approximately 24% to reflect the reduction in fuel expense. The over-recovered balance is below the materiality threshold. On April 30, 2015, the Administrative Law Judge issued an order approving the proposed reduction on an interim basis effective May 1, 2015.

Fuel Reconciliation Proceeding. Pursuant to the 2012 Texas retail rate settlement discussed above, on September 27, 2013, the Company filed an application with the PUCT, designated as PUCT Docket No. 41852, to reconcile $545.3 million of fuel and purchased power expenses incurred during the 45-month period from July 1, 2009 through March 31, 2013. A settlement was reached and a final order was issued by the PUCT on July 11, 2014. The PUCT's final order completes the regulatory review and reconciliation of the Company's fuel expenses for the period through March 31, 2013.

The settlement provides that 100% of margins on non-arbitrage off-system sales (as defined by the settlement) and 50% of margins on arbitrage off-system sales be shared with its Texas customers beginning April 1, 2014. For the period April 1, 2014 through June 30, 2015, the Company's total share of margins assignable to Texas retail jurisdiction, on arbitrage and non-arbitrage off-system sales, may not exceed 10% of the total margins assignable to the Texas retail jurisdiction on all off-system sales. The Company also agreed to file with the PUCT a proceeding to address the reasonableness of the Company's decision to not continue to participate in the Four Corners coal-fired generating Units 4 and 5 after July 2016. It is expected that issues related to the final coal mine closing and reclamation costs will be addressed in that proceeding as well as other issues related to post-participation events such as the asset retirement obligations of the Company related to those two units.

Montana Power Station Approvals. The Company has received a Certificate of Convenience and Necessity ("CCN") from the PUCT to construct four natural gas fired generating units at the Montana Power Station ("the MPS") in El Paso County, Texas. The Company also obtained air permits from the Texas Commission on Environmental Quality ("TCEQ") and the U.S. Environmental Protection Agency ("EPA").

The PUCT has issued final orders approving CCNs for the MPS to Caliente transmission line, MPS In & Out transmission line and the MPS to Montwood transmission line. These transmission lines will connect MPS to the Company’s transmission system for delivery of electricity throughout its service territory. MPS Units 1 and 2 and the MPS to Caliente and MPS In & Out transmission lines became operational in March 2015.

Solar Generation CCN Filing. On April 20, 2015, the Company filed a petition with the PUCT requesting CCN authorization to construct a new 20 megawatt solar-powered generation facility to be located on Fort Bliss in the Company's service territory in Texas. The new facility will be a system resource. The Company has requested a PUCT final order by November 30, 2015 so that the project can be completed before December 31, 2016 to maximize potential tax benefits. This case was assigned PUCT Docket No. 44637. No procedural schedule has yet been issued.

Other Required Approvals. The Company has obtained other required approvals for recovery of fuel costs through fixed fuel factors, other tariffs and approvals as required by the Public Utility Regulatory Act (the "PURA") and the PUCT.

New Mexico Regulatory Matters

2009 New Mexico Stipulation. On December 10, 2009, the NMPRC issued a final order conditionally approving the stipulated rates in NMPRC Case No. 09-00171-UT. The stipulated rates went into effect with January 2010 bills. The stipulated rates provide for an Efficient Use of Energy Factor Rate Rider to recover energy efficiency expenditures which are updated annually for adjustment to the recovery factors.

Fuel and Purchased Power Costs. Fuel and purchased power costs are recovered through base rates and a Fuel and Purchased Power Cost Adjustment Clause (the "FPPCAC") that accounts for changes in the costs of fuel included in base rates. On January 8, 2014, the NMPRC approved the continuation of the FPPCAC without modification in NMPRC Case No. 13-00380-UT. Fuel and purchased power costs are reconciled to actual costs on a monthly basis and recovered or refunded to customers the second succeeding month. The Company recovers costs related to Palo Verde Unit 3 capacity and energy in New Mexico through the FPPCAC as purchased power using a proxy market price approved in the 2014 FPPCAC continuation.

Montana Power Station Approvals. The Company has received a CCN from the NMPRC to construct four units at the MPS and associated transmission lines. The Company also obtained all necessary air permits from the TCEQ and EPA. A final order in NMPRC Case No. 13-00297-UT approving the CCN for MPS Units 3 and 4 was issued on June 11, 2014. MPS Units 1 and 2 and the MPS to Caliente and MPS In & Out transmission lines became operational in March 2015.

Solar Generation CCN Filing. On April 20, 2015, the Company filed a petition with the NMPRC requesting CCN authorization to construct a new 20 megawatt solar-powered generation facility to be located on Fort Bliss in the Company's service territory in Texas. The new facility will be a system resource. The Company has requested a NMPRC final order by November 30, 2015 so that the project can be completed before December 31, 2016 to maximize potential tax benefits. This case was assigned NMPRC Case No. 15-00099-UT. No procedural schedule has yet been issued.

Other Required Approvals. The Company has obtained other required approvals for other tariffs, securities transactions, long-term resource plans, recovery of energy efficiency costs through a base rate rider and other approvals as required by the NMPRC.

Federal Regulatory Matters

Public Service Company of New Mexico's ("PNM") Transmission Rate Case. On December 31, 2012, PNM filed with FERC to change its method of transmission rate recovery for its transmission delivery services from stated rates to formula rates. The Company takes transmission service from PNM and is among the PNM transmission customers affected by PNM's shift to formula rates. On March 1, 2013, the FERC issued an order rejecting in part PNM's filing, and establishing settlement judge and hearing procedures. On March 20, 2015, PNM filed with FERC a settlement agreement and offer of settlement resolving all issues set for hearing in the proceeding. The Company cannot predict the outcome of the case at this time.

Other Required Approvals. The Company has obtained required approvals for rates and tariffs, securities transactions and other approvals as required by the FERC.