Regulatory Matters	3 Months Ended
Regulatory Matters	Mar. 31, 2018
PacifiCorp [Member]
Schedule Of Regulatory Assets and Liabilities [Line Items]
Regulatory Matters	Regulatory Matters Retail Regulated Rates In December 2017, the Tax Cuts and Jobs Act ("2017 Tax Reform") was signed into law, reducing the federal tax rate from 35% to 21%. Accumulated deferred income tax balances were re-measured at the 21% rate, and regulatory liabilities increased reflective of the probability of such balances being passed back to customers. In March 2018, PacifiCorp proposed 1% rate reductions in Utah, Wyoming, and Idaho. PacifiCorp proposed the rate reductions to be effective May 1, 2018, in Utah and June 1, 2018, in Idaho. In April 2018, the Utah Public Service Commission ordered a rate reduction of $61 million effective May 1, 2018, through December 31, 2018, based on a preliminary estimate of the revenue requirement impact of 2017 Tax Reform. This credit will likely be adjusted effective January 1, 2019, when the final rates are approved in the next phase of the proceeding later in 2018. A procedural schedule is expected to be set by the Idaho Public Utilities Commission. PacifiCorp filed a partial settlement with the Wyoming Public Service Commission on April 11, 2018, that provides a rate reduction of approximately 3% beginning July 1, 2018 with the remaining tax savings to be deferred with offsets to other costs. As of March 31, 2018, $53 million was accrued for the estimated potential refund liability attributable to lower customer rates enabled by the benefits of tax reform effective January 1, 2018.
Nevada Power Company [Member]
Schedule Of Regulatory Assets and Liabilities [Line Items]
Regulatory Matters	Regulatory Matters Deferred Energy Nevada statutes permit regulated utilities to adopt deferred energy accounting procedures. The intent of these procedures is to ease the effect on customers of fluctuations in the cost of purchased natural gas, fuel and electricity and are subject to annual prudency review by the PUCN. Under deferred energy accounting, to the extent actual fuel and purchased power costs exceed fuel and purchased power costs recoverable through current rates that excess is not recorded as a current expense on the Consolidated Statements of Operations but rather is deferred and recorded as a regulatory asset on the Consolidated Balance Sheets. Conversely, a regulatory liability is recorded to the extent fuel and purchased power costs recoverable through current rates exceed actual fuel and purchased power costs. These excess amounts are reflected in quarterly adjustments to rates and recorded as cost of fuel, energy and capacity in future time periods. Regulatory Rate Review In June 2017, Nevada Power filed an electric regulatory rate review with the PUCN. The filing supported an annual revenue increase of $29 million, or 2%, but requested no incremental annual revenue relief. In December 2017, the PUCN issued an order which reduced Nevada Power's revenue requirement by $26 million and requires Nevada Power to share 50% of revenues related to equity returns above 9.7%. As a result of the order, Nevada Power recorded expense of $28 million primarily due to the reduction of a regulatory asset to return to customers revenue collected for costs not incurred. The new rates were effective on February 15, 2018. In January 2018, Nevada Power filed a petition for clarification of certain findings and directives in the order and intervening parties filed motions for reconsideration. The PUCN has not yet ruled on the filed motions. Nevada Power cannot predict the timing or ultimate outcome of the PUCN rulings. The Tax Cuts and Jobs Act ("2017 Tax Reform") enacted significant changes to the Internal Revenue Code, including, among other things, a reduction in the U.S. federal corporate income tax rate from 35% to 21%. In February 2018, Nevada Power made a filing with the PUCN proposing a tax rate reduction rider for the lower annual income tax expense anticipated to result from the 2017 Tax Reform for 2018 and beyond. The filing supports an annual rate reduction of $59 million. In March 2018, the PUCN issued an order approving the rate reduction proposed by Nevada Power. The new rates were effective April 1, 2018. The order has extended the procedural schedule to allow parties additional discovery relevant to the 2017 Tax Reform with a hearing scheduled in June 2018. Nevada Power cannot predict the timing or ultimate outcome of further regulatory proceedings. Chapter 704B Applications Chapter 704B of the Nevada Revised Statutes allows retail electric customers with an average annual load of one megawatt ("MW") or more to file with the PUCN an application to purchase energy from alternative providers of a new electric resource and become distribution only service customers. On a case-by-case basis, the PUCN will assess the application and may deny or grant the application subject to conditions, including paying an impact fee, paying on-going charges and receiving approval for specific alternative energy providers and terms. The impact fee and on-going charges are assessed to alleviate the burden on other Nevada customers for the applicant's share of previously committed investments and long-term renewable contracts and are set at a level designed such that the remaining customers are not subjected to increased costs. In October 2016, Wynn became a distribution only service customer and started procuring energy from another energy supplier. In April 2017, Wynn filed a motion with the PUCN seeking relief from the January 2016 order that established the impact fee that was paid in September 2016 and requested the PUCN adopt an alternative impact fee and revise on-going charges associated with retirement of assets and high cost renewable contracts. This request is still pending. In November 2016, Caesars Enterprise Service ("Caesars"), a customer of Nevada Power, filed an application with the PUCN to purchase energy from alternative providers of a new electric resource and become a distribution only service customer of Nevada Power. In March 2017, the PUCN approved the application allowing Caesars to purchase energy from alternative providers subject to conditions, including paying an impact fee. In March 2017, Caesars provided notice that it intends to pay the impact fee and proceed with purchasing energy from alternative providers. In July 2017, Caesars made the required compliance filings and, in September 2017, the PUCN issued an order allowing Caesars to acquire electric energy and ancillary services from another energy supplier and become a distribution only service customer of Nevada Power. In December 2017, Caesars provided notice that it intends to transition eligible meters in the Nevada Power service territory to unbundled electric service in February 2018 at the earliest. In February 2018, Caesars became a distribution only service customer and started procuring energy from another energy supplier. Following the PUCN’s order from March 2017, Caesars’ will pay an impact fee of $44 million in 72 equal monthly payments.
Sierra Pacific Power Company [Member]
Schedule Of Regulatory Assets and Liabilities [Line Items]
Regulatory Matters	Regulatory Matters Deferred Energy Nevada statutes permit regulated utilities to adopt deferred energy accounting procedures. The intent of these procedures is to ease the effect on customers of fluctuations in the cost of purchased natural gas, fuel and electricity and are subject to annual prudency review by the PUCN. Under deferred energy accounting, to the extent actual fuel and purchased power costs exceed fuel and purchased power costs recoverable through current rates that excess is not recorded as a current expense on the Consolidated Statements of Operations but rather is deferred and recorded as a regulatory asset on the Consolidated Balance Sheets. Conversely, a regulatory liability is recorded to the extent fuel and purchased power costs recoverable through current rates exceed actual fuel and purchased power costs. These excess amounts are reflected in quarterly adjustments to rates and recorded as cost of fuel, energy and capacity in future time periods. Regulatory Rate Review The Tax Cuts and Jobs Act ("2017 Tax Reform") enacted significant changes to the Internal Revenue Code, including, among other things, a reduction in the U.S. federal corporate income tax rate from 35% to 21%. In February 2018, Sierra Pacific made a filing with the PUCN proposing a tax rate reduction rider for the lower annual income tax expense anticipated to result from the 2017 Tax Reform for 2018 and beyond. The filing supports an annual rate reduction of $25 million. In March 2018, the PUCN issued an order approving the rate reduction proposed by Sierra Pacific, The new rates were effective April 1, 2018. The order has extended the procedural schedule to allow parties additional discovery relevant to the 2017 Tax Reform with a hearing scheduled in June 2018. Sierra Pacific cannot predict the timing or ultimate outcome of further regulatory proceedings. Chapter 704B Applications Chapter 704B of the Nevada Revised Statutes allows retail electric customers with an average annual load of one megawatt ("MW") or more to file with the PUCN an application to purchase energy from alternative providers of a new electric resource and become distribution only service customers. On a case-by-case basis, the PUCN will assess the application and may deny or grant the application subject to conditions, including paying an impact fee, paying on-going charges and receiving approval for specific alternative energy providers and terms. The impact fee and on-going charges are assessed to alleviate the burden on other Nevada customers for the applicant's share of previously committed investments and long-term renewable contracts and are set at a level designed such that the remaining customers are not subjected to increased costs. In November 2016, Caesars Enterprise Service ("Caesars"), a customer of Sierra Pacific, filed an application with the PUCN to purchase energy from alternative providers of a new electric resource and become a distribution only service customer of Sierra Pacific. In March 2017, the PUCN approved the application allowing Caesars to purchase energy from alternative providers subject to conditions, including paying an impact fee. In March 2017, Caesars provided notice that it intends to pay the impact fee and proceed with purchasing energy from alternative providers. In July 2017, Caesars made the required compliance filings and, in September 2017, the PUCN issued an order allowing Caesars to acquire electric energy and ancillary services from another energy supplier and become a distribution only service customer of Sierra Pacific. In January 2018, Caesars became a distribution only service customer and started procuring energy from another energy supplier for its eligible meters in the Sierra Pacific service territory. Following the PUCN’s order from March 2017, Caesars’ will pay an impact fee of $4 million in 36 monthly payments. In May 2017, Peppermill Resort Spa Casino ("Peppermill"), a customer of Sierra Pacific, filed an application with the PUCN to purchase energy from alternative providers of a new electric resource and become a distribution only service customer of Sierra Pacific. In August 2017, the PUCN approved a stipulation allowing Peppermill to purchase energy from alternative providers subject to conditions, including paying an impact fee. In September 2017, Peppermill provided notice that it intends to pay the impact fee and proceed with purchasing energy from alternative providers. In April 2018, Peppermill paid a one-time impact fee of $3 million and became a distribution only service customer and started procuring energy from another energy supplier.