Environmental Remediation Obligations [Abstract] Schedule of Environmental Loss Contingencies by Site [Table Text Block] Schedule of Environmental Loss Contingencies by Site [Table Text Block] Environmental Regulatory Table [Table Text Block] Environmental Regulatory Table [Table Text Block] Environmental Regulatory Table [Table Text Block] Statement of Financial Position [Abstract] Statement [Table] Statement [Table] Statement, Scenario [Axis] Scenario [Axis] Scenario, Unspecified [Domain] Scenario, Unspecified [Domain] Class of Stock [Axis] Class of Stock [Axis] Class of Stock [Domain] Class of Stock [Domain] Statement [Line Items] Statement [Line Items] Assets [Abstract] Assets [Abstract] Current assets [Abstract] Assets, Current [Abstract] Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Accounts receivable Accounts Receivable, Gross, Current Allowance for uncollectible accounts Allowance for Doubtful Accounts Receivable, Current Accrued unbilled revenue Unbilled Receivables, Current Regulatory assets Regulatory Assets, Current Derivative instruments Derivative Asset, Current Inventories Public Utilities, Inventory Gas reserves Gas Reserves Current Carrying amount as of the balance sheet date of investments in Gas Reserves expected to be recovered within one year or the normal operating cycle if longer. Income taxes receivable Income Taxes Receivable, Current Other current assets Other Assets, Current Total current assets Assets, Current Non-current assets [Abstract] Assets, Noncurrent [Abstract] Property, plant, and equipment Property, Plant and Equipment, Gross Less: Accumulated depreciation Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Total property, plant, and equipment, net Property, Plant and Equipment, Net Gas reserves Gas Reserves Noncurrent Carrying amount as of the balance sheet date of investments in Gas Reserves not expected to be recovered within one year or the normal operating cycle if longer. Regulatory assets Regulatory Assets, Noncurrent Derivative instruments Derivative Asset, Noncurrent Other investments Other Long-term Investments Restricted cash Restricted Cash and Cash Equivalents, Noncurrent Other non-current assets Other Assets, Noncurrent Total non-current assets Assets, Noncurrent Total assets Assets Liabilities and Equity [Abstract] Liabilities and Equity [Abstract] Current liabilities [Abstract] Liabilities, Current [Abstract] Short-term debt Short-term Debt Current maturities of long-term debt Long-term Debt, Current Maturities Accounts payable Accounts Payable, Current Taxes accrued Taxes Payable, Current Interest accrued Interest Payable, Current Regulatory liabilities Regulatory Liability, Current Derivative instruments Derivative Liability, Current Other current liabilities Other Liabilities, Current Total current liabilities Liabilities, Current Long-term debt Long-term Debt, Excluding Current Maturities Deferred credits and other non-current liabilities [Abstract] Deferred Credits and Other Liabilities [Abstract] Deferred tax liabilities Deferred Tax Liabilities, Net, Noncurrent Regulatory liabilities Regulatory Liability, Noncurrent Pension and other postretirement benefit liabilities Pension and Other Postretirement Defined Benefit Plans, Liabilities, Noncurrent Derivative instruments Derivative Liability, Noncurrent Other non-current liabilities Other Liabilities, Noncurrent Total deferred credits and other non-current liabilities Deferred Credits and Other Liabilities, Noncurrent Commitments and contingencies (see Note 13) Commitments and Contingencies Equity [Abstract] Capitalization, Long-term Debt and Equity [Abstract] Common stock - no par value; authorized 100,000 shares; issued and outstanding 27,001, 26,866, and 26,917 at September 30, 2013 and 2012 and December 31, 2012, respectively Common Stock, Value, Issued Retained earnings Retained Earnings (Accumulated Deficit) Accumulated other comprehensive loss Accumulated Other Comprehensive Income (Loss), Net of Tax Total equity Stockholders' Equity Attributable to Parent Total liabilities and equity Liabilities and Equity Summary of Derivative Instruments [Abstract] Schedule of Notional Amounts of Outstanding Derivative Positions [Table Text Block] Schedule of Notional Amounts of Outstanding Derivative Positions [Table Text Block] Income Statement Presentation of Derivative Instruments [Text Block] Derivative Instruments, Gain (Loss) [Table Text Block] Credit Rating Downgrade Scenarios [Text Block] Table Of Estimated Collateral Calls Table [Text Block] Tabular disclosure of estimated collateral demands [Table Text Block] Accounting Changes and Error Corrections [Abstract] Schedule of Error Corrections and Prior Period Adjustment Restatement [Table] Schedule of Error Corrections and Prior Period Adjustment Restatement [Table] Scenario [Axis] Scenario, Previously Reported Scenario, Previously Reported [Member] Restatement Adjustment Restatement Adjustment [Member] Error Corrections and Prior Period Adjustments Restatement Error Corrections and Prior Period Adjustments Restatement [Line Items] Pre-tax decrease to regulatory assets and other income and expense Restatement Adjustment, Pre-Tax Decrease to Regulatory Assets and Other Income and Expense Restatement Adjustment, Pre-Tax Decrease to Regulatory Assets and Other Income and Expense Income Statement [Abstract] Income Statement [Abstract] Other income and expense, net Other Nonoperating Income (Expense) Income before income taxes Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest Income tax expense Income Tax Expense (Benefit) Net income Net Income (Loss) Attributable to Parent Comprehensive income Other Comprehensive Income (Loss), Net of Tax Earnings per share of common stock - basic Earnings Per Share, Basic Earnings per share of common stock - diluted Earnings Per Share, Diluted Balance Sheet [Abstract] Assets, Noncurrent [Abstract] Total non-current assets Total assets Liabilities, Noncurrent [Abstract] Liabilities, Noncurrent [Abstract] Total deferred credits and other non-current liabilities Equity [Abstract] Equity [Abstract] Total equity Total liabilities and equity Public Utility, Property, Plant and Equipment [Table] Public Utility [Axis] Public Utility [Axis] Utility Plant [Domain] Utility Plant [Domain] Utility Plant [Member] Utility Plant [Member] Discloses Utility plant information. Non Utility Plant [Member] Non Utility Plant [Member] Discloses Non-Utility plant information. Property, Plant and Equipment [Line Items] Property, Plant and Equipment [Line Items] Property, Plant and Equipment, Net, by Type [Abstract] Property, Plant and Equipment, Net, by Type [Abstract] Property, Plant, and Equipment, Gross Public Utilities, Property, Plant and Equipment, Construction Work in Progress Public Utilities, Property, Plant and Equipment, Construction Work in Progress Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment General Discussion of Pension and Other Postretirement Benefits [Abstract] Pension and Other Postretirement Benefits Disclosure [Text Block] Pension and Other Postretirement Benefits Disclosure [Text Block] Disclosure Stock Based Compensation [Abstract] -- None. No documentation exists for this element. -- Stock Based Compensation [Text Block] Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Common Stock, Shares, Outstanding Common Stock, Shares, Outstanding Common Stock, Shares Authorized Common Stock, Shares Authorized Long-term Investments [Abstract] Equity Method Investment, Ownership Percentage Equity Method Investment, Ownership Percentage Equity Method Investment, Underlying Equity in Net Assets Equity Method Investment, Underlying Equity in Net Assets Income Tax Disclosure [Abstract] Effective Tax Rate Reconciliation Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] Segment Reporting [Abstract] Segment Information [Text Block] Segment Reporting Disclosure [Text Block] Public Utilities, Property, Plant and Equipment [Abstract] Major Classifications Of Property, Plant And Equipment And Accumulated Depreciation [Text Block] Public Utility Property, Plant, and Equipment [Table Text Block] Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Table] Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Axis] Defined Benefit Plans and Other Postretirement Benefit Plans [Axis] Defined Benefit Plans and Other Postretirement Benefit Plans [Domain] Defined Benefit Plan and Other Postretirement Benefit Plan [Domain] Pension Plans, Defined Benefit [Member] Pension Plan, Defined Benefit [Member] Other Postretirement Benefit Plans, Defined Benefit [Member] Other Postretirement Benefit Plan, Defined Benefit [Member] Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] Total Amounts Reclassified Into Accumulated Other Comprehensive Income Total Amounts Reclassified Into Accumulated Other Comprehensive Income TotalAmountsReclassifiedIntoAccumulatedOtherComprehensiveIncome Other Comprehensive Income (Loss), Amortization, Pension and Other Postretirement Benefit Plans, Net Prior Service Cost Recognized in Net Periodic Benefit Cost, before Tax Other Comprehensive (Income) Loss, Amortization Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Prior Service Cost (Credit), before Tax Other Comprehensive Income (Loss), Reclassification, Pension and Other Postretirement Benefit Plans, Net Gain (Loss) Recognized in Net Periodic Benefit Cost, before Tax Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Gain (Loss), before Tax Other Comprehensive Income Total Reclassifications Before Tax Other Comprehensive Income Total Reclassifications Before Tax Other Comprehensive Income Total Reclassifications Before Tax Other Comprehensive Income (Loss), Amortization, Pension and Other Postretirement Benefit Plans, Net Prior Service Cost Recognized in Net Periodic Pension Cost, Tax Other Comprehensive Income (Loss), Amortization Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Prior Service (Cost) Credit, Tax Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract] Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract] Defined Benefit Plan, Service Cost Defined Benefit Plan, Service Cost Defined Benefit Plan, Interest Cost Defined Benefit Plan, Interest Cost Defined Benefit Plan Expected Return On Plan Assets Defined Benefit Plan, Expected Return on Plan Assets Defined Benefit Plan Amortization Of Net Actuarial Loss Defined Benefit Plan, Future Amortization of Gain (Loss) Defined Benefit Plan, Amortization of Prior Service Cost (Credit) Defined Benefit Plan, Amortization of Prior Service Cost (Credit) Defined Benefit Plan Amortization Of Transition Obligations Defined Benefit Plan, Amortization of Transition Obligations (Assets) Defined Benefit Plan Net Periodic Benefit Cost Defined Benefit Plan, Net Periodic Benefit Cost Defined Benefit Plan Amount Allocated To Construction Defined Benefit Plan Amount Allocated To Construction Net periodic benefit cost allocated to construction. Defined Benefit Plan Net Amount Deferred To Regulatory Balancing Account Defined Benefit Plan Net Amount Deferred To Regulatory Balancing Account Net periodic benefit cost deferred to regulatory balancing account. Defined Benefit Plan Net Amount Charged To Expense Defined Benefit Plan Net Amount Charged To Expense Net periodic benefit cost charged to expense. Qualified Defined Benefit Pension Plan Contributions Pension and Other Postretirement Benefit Contributions Qualified Contributions Expected During Next Fiscal Year Defined Benefit Plan, Estimated Future Employer Contributions in Current Fiscal Year, Description Multiemployer Plan, Period Contributions Multiemployer Plan, Period Contributions Defined Contribution Plan, Cost Recognized Defined Contribution Plan, Cost Recognized Accounting Policies [Abstract] Significant Accounting Policies [Text Block] Significant Accounting Policies [Text Block] Regulatory Assets and Liabilities Disclosure [Abstract] Regulatory Assets Disclosure [Table] Schedule of Regulatory Assets [Table] Regulatory Asset [Axis] Regulatory Asset [Axis] Regulatory Asset [Domain] Regulatory Asset [Domain] Unrealized Loss On Derivatives [Member] Unrealized Loss On Derivatives [Member] Discloses the unrealized loss on derivatives. Pension and Other Postretirement Plans Costs [Member] Pension and Other Postretirement Plans Costs [Member] Pension Balancing [Member] Pension Costs [Member] Income Tax Asset [Member] Deferred Income Tax Charge [Member] Environmental Restoration Costs [Member] Environmental Restoration Costs [Member] Other Regulatory [Member] Other Regulatory Assets (Liabilities) [Member] Regulatory Assets [Line Items] Regulatory Assets [Line Items] Regulatory Assets, Noncurrent Regulatory Assets, Current Schedule of Error Corrections and Prior Period Adjustments Schedule of Error Corrections and Prior Period Adjustments [Table Text Block] Net Periodic Benefit Cost Components Schedule of Net Benefit Costs [Table Text Block] Schedule Of Accumulated Other Comprehensive Income Loss Rollforward [Table Text Block] Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] Long-term Debt, Current and Noncurrent [Abstract] Fair Value Of Long Term Debt Table [Text Block] Schedule of Carrying Values and Estimated Fair Values of Debt Instruments [Table Text Block] Utility Margin [Abstract] Utility Margin (utility operating revenues less utility cost of gas). Revenues Revenues Cost of gas Cost of Revenue Utility margin Utility Margin Utility operating revenues less utility cost of gas. Schedule of Segment Reporting Information, by Segment [Table] Statement, Operating Activities Segment [Axis] Operating Activities [Axis] Segment [Domain] Segments [Domain] Utility Segment [Member] Utility Segment [Member] Discloses Utility segment information. Gas Storage Segment [Member] Gas Storage Segment [Member] Discloses Gas Storage segment information. Other Segment [Member] Other Segments [Member] Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Segment Reporting [Abstract] Depreciation and Amortization Depreciation, Depletion and Amortization, Nonproduction Operating Income (Loss) Operating Income (Loss) Net Income (Loss) Attributable to Parent Payments to Acquire Property, Plant, and Equipment Payments to Acquire Property, Plant, and Equipment Assets Accrual for Environmental Loss Contingencies [Abstract] Environmental Matters [Text Block] Environmental Loss Contingency Disclosure [Text Block] Earnings Per Share [Abstract] EPS Calculation Table Text Block Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Statement of Cash Flows [Abstract] Operating activities [Abstract] Net Cash Provided by (Used in) Operating Activities [Abstract] Adjustments to reconcile net income to cash provided by operations [Abstract] Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Depreciation and amortization Deferred tax liabilities Increase (Decrease) in Income Taxes Payable Non-cash expenses related to qualified defined benefit pension plans Pension Expense Contributions to qualified defined benefit pension plans Pension Contributions Deferred environmental expenditures, net of recoveries Environmental Expense and Liabilities Other Other Noncash Income Changes in assets and liabilities [Abstract] Increase (Decrease) in Operating Capital [Abstract] Receivables Increase (Decrease) in Accounts and Other Receivables Inventories Increase (Decrease) in Inventories Taxes accrued Increase (Decrease) in Income Taxes Receivable Accounts payable Increase (Decrease) in Accounts Payable Interest accrued Increase (Decrease) in Interest Payable, Net Deferred gas costs Increase (Decrease) in Deferred Gas Cost Other, net Increase (Decrease) in Other Operating Liabilities Cash provided by operating activities Net Cash Provided by (Used in) Operating Activities Investing activities [Abstract] Net Cash Provided by (Used in) Investing Activities [Abstract] Capital expenditures Utility gas reserves Payments To Acquire Utility Gas Reserves Payments to acquire utility gas reserves Proceeds from sale of assets Proceeds from Sale of Property, Plant, and Equipment Other Payments for (Proceeds from) Other Investing Activities Cash used in investing activities Net Cash Provided by (Used in) Investing Activities Financing activities [Abstract] Net Cash Provided by (Used in) Financing Activities [Abstract] Common stock issued, net Proceeds from Issuance of Common Stock Long-term debt issued Proceeds from Issuance of Long-term Debt Long-term debt retired Repayments of Long-term Debt Change in short-term debt Proceeds from (Repayments of) Short-term Debt Cash dividend payments on common stock Payments of Ordinary Dividends, Common Stock Other Proceeds from (Payments for) Other Financing Activities Cash used in financing activities Net Cash Provided by (Used in) Financing Activities Increase (decrease) in cash and cash equivalents Cash and Cash Equivalents, Period Increase (Decrease) Cash and cash equivalents, beginning of period Cash and cash equivalents, end of period Supplemental disclosure of cash flow information [Abstract] Supplemental Cash Flow Information [Abstract] Interest paid Interest Paid Income taxes paid Income Taxes Paid Debt Disclosure [Abstract] Debt [Text Block] Debt Disclosure [Text Block] Schedule of Segment Reporting Information, by Segment [Table Text Block] Schedule of Segment Reporting Information, by Segment [Table Text Block] Utility Margin [Table Text Block] Utility Margin [Table Text Block] [Table Text Block] Utility margin (utility operating revenues less utility cost of gas). Revision [Text Block] Accounting Changes and Error Corrections [Text Block] Effective Income Tax Rate Reconciliation, Percent [Abstract] Federal Statutory Tax Rate Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent Current State Income Tax, Net Of Federal Tax Benefit Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent Amortization Of Investment And Energy Tax Credits Effective Income Tax Rate Reconciliation, Tax Credit, Percent Differences Required To Be Flowed Through By Regulatory Commissions Differences Required To Be Flowed Through By Regulatory Commissions Differences required to be flowed-through by regulatory commissions Gains On Company And Trust Owned Life Insurance Effective Income Tax Rate Reconciliation, Nondeductible Expense, Life Insurance, Percent One-Time Tax Adjustment One-Time Tax Adjustment One-Time Tax Adjustment Other - Net Effective Income Tax Rate Reconciliation, Other Adjustments, Percent Effective Income Tax Rate Effective Income Tax Rate Reconciliation, Percent One-time, After-tax Charge One-time, After-tax Charge One-time, After-tax Charge Gas Reserves Table [Abstract] -- None. No documentation exists for this element. -- Gas Reserves Table [Text Block] Gas Reserves Table [Text Block] Tabular disclosure of information pertaining to gas reserves. Earnings Per Share, Diluted, Other Disclosures [Abstract] Antidilutive Shares Excluded from Net Income Per Diluted Common Share Calculation Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Average common shares outstanding - basic Weighted Average Number of Shares Outstanding, Basic Additional shares for stock based compensation plans Weighted Average Number Diluted Shares Outstanding Adjustment Average common shares outstanding - diluted Weighted Average Number of Shares Outstanding, Diluted Investments [Abstract] Investment [Text Block] Investment [Text Block] Gas Reserves [Abstract] -- None. No documentation exists for this element. -- Gas Reserves [Text Block] Gas Reserves Disclosure [Text Block] Gas Reserves Disclosure [Text Block] Subsequent Events [Abstract] Subsequent Event, Description Subsequent Event, Description Operating revenues [Abstract] Revenues [Abstract] Operating revenues Operating expenses [Abstract] Operating Expenses [Abstract] Operations and maintenance Utilities Operating Expense, Maintenance, Operations, and Other Costs and Expenses General taxes Taxes, Miscellaneous Total operating expenses Operating Expenses Income (loss) from operations Interest expense, net Interest Expense Income (loss) before income taxes Income tax expense (benefit) Net income (loss) Other comprehensive income [Abstract] Other Comprehensive Income (Loss), Net of Tax [Abstract] Amortization of non-qualified employee benefit plan liability, net of taxes of $152 and $108 for the three months and $454 and $325 for the nine months ended September 30, 2013 and 2012, respectively Comprehensive income (loss) Average common shares outstanding [Abstract] Weighted Average Number of Shares Outstanding, Diluted [Abstract] Basic Diluted Earnings (loss) per share of common stock [Abstract] Basic Diluted Dividends declared per share of common stock Common Stock, Dividends, Per Share, Declared Description of Credit Risk Related to Contingent Features [Abstract] Description of Credit Risk Related to Contingent Features [Abstract] Credit Rating Downgrade Scenarios [Table] Credit Rating Downgrade Scenarios [Table] Tablular disclosure of credit quality indicators related to derivative instruments. Credit Rating Downgrade Scenarios [Axis] Credit Rating Source [Axis] Credit Rating Source [Domain] Credit Rating Source [Domain] Moody's, A3 Rating [Member] Moody's, A3 Rating [Member] Moody's, Baa1 Rating [Member] Moody's, Baa1 Rating [Member] Moody's, Baa2 Rating [Member] Moody's, Baa2 Rating [Member] Moody's, Baa3 Rating [Member] Moody's, Baa3 Rating [Member] Speculative [Member] Speculative [Member] Credit rating below Baa3 as defined by the external credit rating agency, Moody's. Description Of Credit Risk Related Contingent Features [Line Items] Description Of Credit Risk Related Contingent Features [Line Items] Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. With Adequate Assurance Calls With Adequate Assurance Calls Estimated level of collateral demands with adequate assurance calls Without Adequate Assurance Calls Without Adequate Assurance Calls Estimated level of collateral demands without adequate assurance calls Schedule of Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Table] Schedule of Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Table] Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items] Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items] Earnings Per Share [Text Block] Earnings Per Share [Text Block] LTIP Paragraph 1 [Abstract] LTIP Paragraph 1 [Abstract] Common stock was authorized for grants under the LTIP Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Period Increase (Decrease) Weighted-average per share grant date fair value of unvested shares Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value Fair value pricing model LTIP Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Method Used Stock price on valuation date Share Based Compensation Arrangement By Share Based Payment Award Market Value On Valuation Date Stock price on the Long Term Incentive Plan (LTIP) grant date Performance term (in years) Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term Quarterly Dividends Paid Per Share Quarterly Dividends Paid Per Share Quarterly Dividends Paid Per Share Expected dividend yield Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate Dividend Discount Factor Dividend Discount Factor Dividend Discount Factor LTIP Paragraph 2 [Abstract] -- None. No documentation exists for this element. -- Share Based Compensation Arrangement By Share Based Payment Award Grant Date LTIP & RSU ShareBasedCompensationArrangementByShareBasedPaymentAwardGrantDateLTIP&RSU Share Based Compensation Arrangement By Share Based Payment Award Grant Date LTIP & RSU Shares Granted Under RSU Shares Granted Under RSU Shares Granted Under RSU Stock Price On Restricted Stock Unit Grant Date, Minimum Stock Price On Restricted Stock Unit Grant Date, Minimum Stock Price On Restricted Stock Unit Grant Date, Minimum Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Share-based Awards Other than Options SOP Paragraph 1 [Abstract] SOP Paragraph 1 [Abstract] Unrecognized compensation cost, options Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized Unrecognized compensation cost, period for recognition Unrecognized compensation cost, period for recognition The maximum vesting term over which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition. Organization, Consolidation and Presentation of Financial Statements [Abstract] Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Gas Reserves Percent Gas Supplies YTD Gas Reserves Percent Gas Supplies YTD Percent of total gas supplies that were from gas reserves. Gas Reserves, Current Gas Reserves Noncurrent Gross Gas Reserves Noncurrent Gross Gross carrying amount as of the balance sheet date of investments in Gas Reserves expected to be recovered in longer than one year. Gas Reserves Amortization Gas Reserves Amortization Cumulative regulatory amortization of gas reserves investment. Total Gas Reserves Total Gas Reserves Total gas reserves net of amortization. Deferred Taxes Related To Gas Reserves Deferred Taxes Related To Gas Reserves Deferred taxes related to gas reserves Net Gas Reserves Investment Net Gas Reserves Investment Gas reserves investment net of amortization and deferred taxes. General Discussion of Derivative Instruments and Hedging Activities [Abstract] Changes In Fair Value As Deferred Regulatory Assets Or Liabilities In Percentage Changes In Fair Value As Deferred Regulatory Assets Or Liabilities In Percentage Deferral percentage for any gains and losses as regulatory assets or liabilities Changes In Fair Value Deferred As Income Statement For Contracts Not Qualifying For Hedge Accounting And To Other Comprehensive Income For Contracts Qualifying For Hedge Accounting Changes In Fair Value Deferred As Income Statement For Contracts Not Qualifying For Hedge Accounting And To Other Comprehensive Income For Contracts Qualifying For Hedge Accounting Percentage of gains or losses that are not deferred as regulatory assets or liabilities. This percentage impact earnings. Target Hedge Percentage Target Hedge Percentage Target Hedge Percentage for the upcoming gas year. Unrealized Loss On Derivatives Unrealized Loss On Derivatives The unrealized loss on derivative instruments as of the balance sheet date Derivative Asset, Fair Value, Net Derivative Asset, Fair Value, Amount Not Offset Against Collateral Derivative Liability, Fair Value, Net Derivative Liability, Fair Value, Amount Not Offset Against Collateral Derivative, Loss on Derivative Derivative, Loss on Derivative Derivative Fair Value Of Derivative Net Derivative, Fair Value, Net Derivative Instruments, Gain (Loss) [Table] Derivative Instruments, Gain (Loss) by Income Statement Location [Axis] Income Statement Location [Axis] Income Statement and Other Comprehensive Income (Loss) Location [Domain] Income Statement Location [Domain] Natural Gas Commodity [Member] Commodity Contract [Member] Foreign Currency [Member] Foreign Exchange Contract [Member] Derivative [Line Items] Derivative [Line Items] Notional Amount of Derivatives [Abstract] Notional Disclosures [Abstract] Derivative, Nonmonetary Notional Amount Derivative, Nonmonetary Notional Amount Notional Amount of Foreign Currency Derivatives Derivative, Notional Amount Summary of Derivative Instruments [Abstract] Cost of sales Other comprehensive loss Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Less:Amounts deferred to regulatory accounts on balance sheet Amounts Deferred To Regulatory Accounts The amount of derivatives deferred to the individual regulatory noncurrent liability on the balance sheet. Total gain (loss) in pre-tax earnings Gain (Loss) on Derivative Instruments, Net, Pretax Schedule of Regulatory Assets [Table Text Block] Schedule of Regulatory Assets [Table Text Block] Schedule of Regulatory Liabilities [Table Text Block] Schedule of Regulatory Liabilities [Table Text Block] Quarterly Financial Information Disclosure [Abstract] Document Information [Table] Document Information [Table] Document Information, Document [Axis] Document Information, Document [Axis] Document [Domain] Document [Domain] Document Information [Line Items] Document Information [Line Items] Document Type Document Type Document Period End Date Document Period End Date Amendment Flag Amendment Flag Current Fiscal Year End Date Current Fiscal Year End Date Entity Central Index Key Entity Central Index Key Entity Current Reporting Status Entity Current Reporting Status Entity Filer Category Entity Filer Category Entity Registrant Name Entity Registrant Name Entity Voluntary Filers Entity Voluntary Filers Entity Well-known Seasoned Issuer Entity Well-known Seasoned Issuer Entity Common Stock Shares Outstanding Entity Common Stock, Shares Outstanding Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Schedule of Regulatory Liabilities [Table] Schedule of Regulatory Liabilities [Table] Regulatory Liability [Axis] Regulatory Liability [Axis] Regulatory Liability [Domain] Regulatory Liability [Domain] Gas Costs Payable [Member] Asset Recoverable Gas Costs [Member] Unrealized Gain On Derivatives [Member] Deferred Derivative Gain (Loss) [Member] Accrued Asset Removal Costs [Member] Removal Costs [Member] Regulatory Liabilities [Line Items] Regulatory Liabilities [Line Items] Current Regulatory Liabilities Environmental Regulatory Table [Abstract] Environmental Regulatory Table [Abstract] Cash Paid for Environmental Sites Cash Paid for Environmental Sites Cash Paid for Environmental Sites Damages Sought On Environmental Claims Loss Contingency, Damages Sought, Value Portland Harbor draft FS range Loss Contingency Range Of Possible Loss Portland Harbor Describes the estimated range of loss from the specified contingency when no single amount within the range appears to be a better estimate than any other amount within the range, may disclose the factors that could cause the estimate to change, and may indicate that a material change in estimate might occur based on a reasonably possible change in circumstances. Portland Harbor draft FS liability. Portland Harbor Number Of Potentially Responsible Parties Portland Harbor Number Of Potentially Responsible Parties Portland Harbor Number Of Potentially Responsible Parties Gasco Siltronic Sediments draft EE/CA range Loss Contingency Range Of Possible Loss Gasco Siltronic -- None. No documentation exists for this element. -- Gasco Siltronic Sediments Project Liability Gasco Siltronic Sediments Project Liability Discloses the estimated liability related to the Gasco Siltronic Sediments Project environmental remediation. Gasco Siltronic Sediments Other Liability Gasco Siltronic Sediments Other Liability Discloses the estimated liability related to the Gasco Siltronic Sediments Project other costs such as design, investigation, oversight and clean-up work. Gasco Groundwater Source Control range Loss Contingency Range Of Possible Loss Gasco Groundwater Source Control Describes the estimated range of loss from the specified contingency when no single amount within the range appears to be a better estimate than any other amount within the range, may disclose the factors that could cause the estimate to change, and may indicate that a material change in estimate might occur based on a reasonably possible change in circumstances. Gasco Groundwater Source Control liability. Gasco Groundwater Source Control construction costs Gasco Groundwater Source Control construction costs Gasco Groundwater Source Control construction costs included in Oregon rates Environmental Activity [Table] A table of environmental activities. Environmental Activity [Axis] Environmental Remediation Site [Axis] Environmental Remediation Site [Domain] Environmental Remediation Site [Domain] Gasco Siltronic Sediments [Member] Gasco Siltronic Sediments [Member] Discloses the details related to the Gasco Siltronic Sediments environmental site Portland Harbor Other [Member] Portland Harbor Other [Member] Discloses the details related to the Portland Harbor Other environmental site Gasco Upland [Member] Gasco Upland [Member] iscloses the details related to the Gasco environmental site Siltronic Upland [Member] Siltronic Upland [Member] Discloses the details related to the Siltronic Upland environmental site Central Service Center [Member] Central Service Center [Member] Discloses the details related to the Central Service Center environmental site Front Street [Member] Front Street [Member] Discloses the details related to the Front Street environmental site Oregon Steel Mills [Member] Oregon Steel Mills [Member] Discloses the details related to Oregon Steel Mills. Environmental Activity [Line Items] Environmental Activity [Line Items] Line items represent environmental sites included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. Accrual for Environmental Loss Contingencies [Abstract] Environmental Noncurrent Liabilities Accrued Environmental Loss Contingencies, Noncurrent Environmental Current Liabilities Accrued Environmental Loss Contingencies, Current Share-based Compensation [Abstract] LTIP Assumptions [Table Text Block] Table Of Assumptions For L T I P Monte Carlo Pricing Option Table [Text Block] Tabular disclosure of key inputs for Long Term Incentive Plan (LTIP) Monte-Carlo Pricing Option model [Table Text Block] Amortization of non-qualified employee benefit plan liability, net of taxes of $152 and $108 for the three months and $454 and $325 for the nine months ended September 30, 2013 and 2012, respectively Subsequent Events [Text Block] Subsequent Events [Text Block] Long-term Debt, Unclassified [Abstract] Carrying Amount Medium-term Notes Estimated Fair Value Debt Instrument, Fair Value Disclosure Short-term Debt [Abstract] Commercial Paper, Maximum Maturity Commercial Paper, Maximum Maturity Commercial Paper, Maximum Maturity Commercial Paper, Average Maturity Commercial Paper, Average Maturity Commercial Paper, Average Maturity Debt Instrument, Description Long-term Debt, Maturities, Repayment Terms Derivative Instrument Detail [Abstract] Derivative Instruments [Text Block] Derivative Instruments and Hedging Activities Disclosure [Text Block] Property, Plant and Equipment [Abstract] Property, Plant and Equipment Disclosure [Text Block] Property, Plant and Equipment Disclosure [Text Block] Income Tax Disclosure [Text Block] Income Tax Disclosure [Text Block]