Compensation and Retirement Disclosure [Abstract] Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Table] Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Table] Related Party [Axis] Related Party [Axis] Related Party [Domain] Related Party [Domain] NV Energy [Member] NV Energy, Inc. [Member] Represents NV Energy, Inc. and its subsidiaries. Defined Benefit Plans and Other Postretirement Benefit Plans [Axis] Defined Benefit Plans and Other Postretirement Benefit Plans [Axis] Defined Benefit Plan and Other Postretirement Benefit Plan [Domain] Defined Benefit Plan and Other Postretirement Benefit Plan [Domain] Qualified Pension Plans [Member] Qualified Pension Plans [Member] Qualified Pension Plans [Member] Non-Qualified Pension Plans [Member] Nonqualified Pension Plans [Member] Nonqualified Pension Plans [Member] Other Postretirement Plans [Member] Other Postretirement Benefit Plan, Defined Benefit [Member] Balance Sheet Location [Axis] Balance Sheet Location [Axis] Balance Sheet Location [Domain] Balance Sheet Location [Domain] Other assets [Member] Other Noncurrent Assets [Member] Customer deposits and other [Member] Customer Deposits and Other [Member] Customer Deposits and Other [Member] Other long-term liabilities [Member] Other Noncurrent Liabilities [Member] Employee Benefit Plans [Line Items] Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] Amounts Recognized in Balance Sheet [Abstract] Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract] Other assets Defined Benefit Plan, Assets for Plan Benefits, Noncurrent Customer deposits and other Pension and Other Postretirement Defined Benefit Plans, Current Liabilities Other long-term liabilities Pension and Other Postretirement Defined Benefit Plans, Liabilities, Noncurrent Statement of Cash Flows [Abstract] Cash flows from operating activities: Net Cash Provided by (Used in) Operating Activities [Abstract] Net income Net Income (Loss) Attributable to Parent Adjustments to reconcile net income to net cash flows from operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Depreciation and amortization Utilities Operating Expense, Depreciation and Amortization Deferred income taxes and amortization of investment tax credits Deferred Income Taxes and Tax Credits Allowance for equity funds Increase (Decrease) in Allowance for Equity Funds Used During Construction Amortization of deferred energy Amortization of Deferred Charges Deferred energy Deferred Energy Change Deferred Energy Change Amortization of other regulatory assets Amortization of Regulatory Asset Other, net Other Noncash Income (Expense) Changes in other operating assets and liabilities: Increase (Decrease) in Operating Capital [Abstract] Accounts receivable and other assets Increase (Decrease) in Accounts Receivable and Other Operating Assets Inventories Increase (Decrease) in Inventories Accounts payable and other liabilities Increase (Decrease) in Accounts Payable and Other Operating Liabilities Net cash flows from operating activities Net Cash Provided by (Used in) Operating Activities Cash flows from investing activities: Net Cash Provided by (Used in) Investing Activities [Abstract] Capital expenditures Payments to Acquire Property, Plant, and Equipment Contributions in aid of construction and customer advances Proceeds from Contribution in Aid of Construction and Customer Advances Proceeds from Contribution in Aid of Construction and Customer Advances Net cash flows from investing activities Net Cash Provided by (Used in) Investing Activities Net change in cash and cash equivalents Cash and Cash Equivalents, Period Increase (Decrease) Cash and cash equivalents at beginning of period Cash and Cash Equivalents, at Carrying Value Cash and cash equivalents at end of period Schedule of Amounts Recognized in Balance Sheet Schedule of Amounts Recognized in Balance Sheet [Table Text Block] Statement of Stockholders' Equity [Abstract] Statement [Table] Statement [Table] Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Common Stock Common Stock [Member] Other Paid-in Capital Additional Paid-in Capital [Member] Retained Earnings Retained Earnings [Member] Accumulated Other Comprehensive Loss, Net Accumulated Other Comprehensive Income (Loss) [Member] Statement [Line Items] Statement [Line Items] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Balance (shares) Common Stock, Shares, Outstanding Balance Stockholders' Equity Attributable to Parent Other Stockholders' Equity, Other Balance (shares) Balance Segment Reporting [Abstract] Schedule of Segment Reporting Information, by Segment Schedule of Segment Reporting Information, by Segment [Table Text Block] Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Segments [Axis] Segments [Axis] Segments [Domain] Segments [Domain] Electric Operations [Member] Electric Operations [Member] Electric Operations [Member] Natural Gas Operations [Member] Natural Gas Operations [Member] Natural Gas Operations [Member] Corporate, Non-Segment [Member] Corporate, Non-Segment [Member] Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Number of reportable segments Number of Reportable Segments Electric Electric Domestic Regulated Revenue Natural gas Gas Domestic Regulated Revenue Revenues Revenues Cost of fuel, energy and capacity Cost of Services, Energy Services Natural gas purchased for resale Cost of Purchased Oil and Gas Gross margin Gross Profit Operating and maintenance expense Utilities Operating Expense, Maintenance and Operations Property and other taxes Utilities Operating Expense, Taxes Interest expense, net of allowance for debt funds Interest Expense Allowance for equity funds Public Utilities, Allowance for Funds Used During Construction, Capitalized Cost of Equity Other, net Other Nonoperating Income (Expense) Income before income tax expense Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest Assets Assets Organization, Consolidation and Presentation of Financial Statements [Abstract] Organization and Operations Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Regulated Operations [Abstract] Public Utilities General Disclosures [Table] Public Utilities General Disclosures [Table] Business Acquisition [Axis] Business Acquisition [Axis] Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree [Domain] MEHC Merger NV Energy Transaction [Member] Represents amounts associated with the NV Energy Transaction [Member] Regulatory Agency [Axis] Regulatory Agency [Axis] Regulatory Agency [Domain] Regulatory Agency [Domain] Public Utilities Commission, Nevada [Member] Public Utilities Commission, Nevada [Member] Public Utilities Commission, Nevada [Member] Federal Energy Regulatory Commission [Member] Federal Energy Regulatory Commission [Member] Federal Energy Regulatory Commission [Member] Public Utilities, General Disclosures [Line Items] Public Utilities, General Disclosures [Line Items] Recovery of loss on revenues Regulatory Stipulation, Lost Revenue Limit Regulatory stipulation that limits the amount of lost revenues that can be requested. Customer refund liability, current Customer Refund Liability, Current Requested rate increase (decrease), amended, amount Public Utilities, Requested Rate Increase (Decrease), Amended, Amount Fair Value Disclosures [Abstract] Fair Value Measurements Fair Value Disclosures [Text Block] Property, Plant and Equipment, Net [Abstract] Schedule of Property, Plant and Equipment [Table] Public Utility, Property, Plant and Equipment [Table] Public Utility [Axis] Public Utility [Axis] Utility Plant [Domain] Utility Plant [Domain] Electric Plant [Member] Electricity Generation Plant, Non-Nuclear [Member] Gas Plant [Member] Natural Gas Processing Plant [Member] Property, Plant and Equipment [Line Items] Public Utility, Property, Plant and Equipment [Line Items] Utility plant in-service: Public Utilities, Property, Plant and Equipment, Plant in Service [Abstract] Generation Public Utilities, Property, Plant and Equipment, Generation or Processing Distribution Public Utilities, Property, Plant and Equipment, Distribution Transmission Public Utilities, Property, Plant and Equipment, Transmission Intangible plant Public Utilities, Property, Plant and Equipment, Other Property, Plant and Equipment Common general Public Utilities, Property, Plant and Equipment, Common Utility plant in-service Public Utilities, Property, Plant and Equipment, Plant in Service, Excluding Construction Work In Progress Public Utilities, Property, Plant and Equipment, Plant in Service, Excluding Construction Work In Progress Accumulated depreciation and amortization Public Utilities, Property, Plant and Equipment, Accumulated Depreciation Utility plant in-service, net Public Utilities, Property, Plant and Equipment, Net, Excluding Construction Work In Progress Public Utilities, Property, Plant and Equipment, Net, Excluding Construction Work In Progress Construction work-in-progress Public Utilities, Property, Plant and Equipment, Construction Work in Progress Property, plant and equipment, net Public Utilities, Property, Plant and Equipment, Net Property, Plant and Equipment, Net Property, Plant and Equipment Disclosure [Text Block] Segment Information Segment Reporting Disclosure [Text Block] Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Commitments Contingencies and Guarantees [Text Block] Fair Value, by Balance Sheet Grouping Fair Value, by Balance Sheet Grouping [Table Text Block] Statement of Financial Position [Abstract] ASSETS Assets [Abstract] Current assets: Assets, Current [Abstract] Cash and cash equivalents Accounts receivable, net Accounts Receivable, Net, Current Inventories Inventory, Net Regulatory assets Regulatory Assets, Current Deferred income taxes Deferred Tax Assets, Net of Valuation Allowance, Current Other current assets Other Assets, Current Total current assets Assets, Current Property, plant and equipment, net Regulatory assets Regulatory Assets, Noncurrent Other assets Other Assets, Noncurrent Total assets LIABILITIES AND SHAREHOLDER'S EQUITY Liabilities and Equity [Abstract] Current liabilities: Liabilities, Current [Abstract] Accounts payable Accounts Payable, Current Accrued interest Interest Payable, Current Accrued property, income and other taxes Taxes Payable, Current Accrued employee expenses Employee-related Liabilities, Current Regulatory liabilities Regulatory Liability, Current Current portion of long-term debt Long-term Debt and Capital Lease Obligations, Current Customer deposits and other Other Liabilities, Current Total current liabilities Liabilities, Current Long-term debt Long-term Debt and Capital Lease Obligations Regulatory liabilities Regulatory Liability, Noncurrent Deferred income taxes Deferred Tax Liabilities, Net, Noncurrent Other long-term liabilities Other Liabilities, Noncurrent Total liabilities Liabilities Commitments and contingencies (Note 7) Commitments and Contingencies Shareholder's Equity: Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] Common stock - $3.75 stated value, 20,000,000 shares authorized and 1,000 issued and outstanding Common Stock, Value, Issued Other paid-in capital Additional Paid in Capital, Common Stock Accumulated deficit Retained Earnings (Accumulated Deficit) Accumulated other comprehensive loss, net Accumulated Other Comprehensive Income (Loss), Net of Tax Total shareholder's equity Total liabilities and shareholder's equity Liabilities and Equity Document and Entity Information [Abstract] Document and Entity Information [Abstract] Entity Registrant Name Entity Registrant Name Entity Central Index Key Entity Central Index Key Current Fiscal Year End Date Current Fiscal Year End Date Entity Well-known Seasoned Issuer Entity Well-known Seasoned Issuer Entity Voluntary Filers Entity Voluntary Filers Entity Current Reporting Status Entity Current Reporting Status Entity Filer Category Entity Filer Category Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Entity Public Float Entity Public Float Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Document Type Document Type Amendment Flag Amendment Flag Document Period End Date Document Period End Date Regulatory Assets and Liabilities Disclosure [Abstract] Regulatory Matters Schedule of Regulatory Assets and Liabilities [Text Block] Employee Benefit Plans Pension and Other Postretirement Benefits Disclosure [Text Block] New Accounting Pronouncements [Abstract] New Accounting Pronouncements [Abstract] Accounting Changes [Text Block] Accounting Changes [Text Block] Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Fair Value, Hierarchy [Axis] Fair Value, Hierarchy [Axis] Fair Value, Measurements, Fair Value Hierarchy [Domain] Fair Value Hierarchy [Domain] Level 2 [Member] Fair Value, Inputs, Level 2 [Member] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Long-term debt Long-term Debt Long-term debt, fair value Long-term Debt, Fair Value Property, Plant, and Equipment, Net Public Utility Property, Plant, and Equipment [Table Text Block] Income Statement [Abstract] Operating revenue: Revenues [Abstract] Total operating revenue Operating costs and expenses: Utilities Operating Expense [Abstract] Total operating costs and expenses Costs and Expenses Operating income Operating Income (Loss) Other income (expense): Nonoperating Income (Expense) [Abstract] Interest expense, net of allowance for debt funds Allowance for equity funds Other, net Total other income (expense) Nonoperating Income (Expense) Income before income tax expense Income tax expense Income Tax Expense (Benefit) Net income Common stock, stated value per share Common Stock, Par or Stated Value Per Share Common stock, shares authorized Common Stock, Shares Authorized Common stock, shares issued Common Stock, Shares, Issued Common stock, shares outstanding Loss Contingencies [Table] Loss Contingencies [Table] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Domain] Property, Plant and Equipment, Type [Domain] ON Line Transmission Line [Member] ON Line Transmission Line [Member] ON Line Transmission Line [Member] Parties to Contractual Arrangement [Axis] Parties to Contractual Arrangement [Axis] Parties to Contractual Arrangement [Domain] Parties to Contractual Arrangement [Domain] Nevada Power Company [Member] Nevada Power Company [Member] Represents Nevada Power Company. Sierra Pacific Power Company [Member] Sierra Pacific Power Company [Member] Represents Sierra Pacific Power Company. Jointly Owned Utility Plant, Name [Axis] Jointly Owned Utility Plant, Name [Axis] Identifies the name of a jointly owned utility plant. Jointly Owned Utility, Name [Domain] Jointly Owned Utility, Name [Domain] Names of a jointly owned utility plant. Valmy Generating Station [Member] Valmy Generating Station [Member] 261 MW nominally rated Valmy Generating Station Legal Entity [Axis] Legal Entity [Axis] Entity [Domain] Entity [Domain] Idaho Power Company [Member] Idaho Power Company [Member] Idaho Power Company [Member] Newmont Nevada Energy Investment, LLC [Member] Newmont Nevada Energy Investment, LLC [Member] Newmont Nevada Energy Investment, LLC [Member] TS Power Plant [Member] TS Power Plant [Member] TS Power Plant [Member] Litigation Case [Axis] Litigation Case [Axis] Litigation Case [Domain] Litigation Case [Domain] Subrogation Lawsuit [Member] Subrogation Lawsuit [Member] Subrogation Lawsuit [Member] Individual Claimant [Member] Individual Claimant [Member] Individual Claimant [Member] One Of Individual Claimants [Member] One Of Individual Claimants [Member] One Of Individual Claimants [Member] Loss Contingency Nature [Axis] Loss Contingency Nature [Axis] Loss Contingency, Nature [Domain] Loss Contingency, Nature [Domain] Caughlin Fire [Member] Damage from Fire, Explosion or Other Hazard [Member] Loss Contingencies [Line Items] Loss Contingencies [Line Items] Company share Jointly Owned Utility Plant, Proportionate Ownership Share Coal-fired power plant capacity Coal-Fired Power Plant Capacity Coal-Fired Power Plant Capacity Amount of bond posted Loss Contingency, Amount of Bond Posted Loss Contingency, Amount of Bond Posted Subsynchronous resonance costs Subsynchronous resonance costs Costs of studies conducted for Subsynchronous resonance Installation costs of protection equipment Installation costs of protection equipment Installation costs of protection equipment Utilities Aggregate Share Transmission Line Project Utilities Aggregate Share Transmission Line Project Utilities Aggregate Share Transmission Line Project Number of lawsuits Loss Contingency, Pending Claims, Number Loss Contingency, Number of Plaintiffs Loss Contingency, Number of Plaintiffs