Entity Central Index Key Document document and entity information abstract. Document And Entity Information [Abstract] Document Type Document Type Amendment Flag Amendment Flag Document Period End Date Document Period End Date Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Trading Symbol Trading Symbol Entity Registrant Name Entity Registrant Name Entity Central Index Key Current Fiscal Year End Date Current Fiscal Year End Date Entity Filer Category Entity Filer Category Entity Common Stock, Shares Outstanding Entity Common Stock Shares Outstanding Tangible assets that are held by an entity for use other than utility production; net of accumulated depreciation. Deferred credits and regulatory liabilities. Redeemable preferred stock at redemption value. Statement Of Financial Position [Abstract] ASSETS Assets [Abstract] Property plant and equipment Property Plant And Equipment Net [Abstract] Utility plant—at original cost, net of accumulated depreciation of $4,062,270 at March 31 and $3,991,680 at December 31 Public Utilities Property Plant And Equipment Net Nonutility property, net of accumulated depreciation of $239,246 at March 31 and $248,341 at December 31 Non Utility Property Net Total property, plant and equipment Property Plant And Equipment Net Current assets Assets Current [Abstract] Cash and cash equivalents Cash And Cash Equivalents At Carrying Value Restricted funds Restricted Cash And Cash Equivalents At Carrying Value Accounts receivable Accounts Receivable Gross Current Allowance for uncollectible accounts Valuation Allowances And Reserves Balance Unbilled revenues Unbilled Receivables Current Income taxes receivable Income Taxes Receivable Materials and supplies Inventory Raw Materials And Supplies Deferred income taxes Deferred Tax Assets Liabilities Net Current Other Other Assets Current Total current assets Assets Current Regulatory and other long-term assets Regulated Entity Other Assets Noncurrent [Abstract] Regulatory assets Regulatory Assets Noncurrent Restricted funds Restricted Cash And Cash Equivalents Noncurrent Goodwill Goodwill Other Other Assets Noncurrent Total regulatory and other long-term assets Regulated Entity Other Assets Noncurrent TOTAL ASSETS Assets Utility plant, accumulated depreciation Public Utilities Property Plant And Equipment Accumulated Depreciation Nonutility property, accumulated depreciation Accumulated Depreciation Depletion And Amortization Property Plant And Equipment Deferred credits and regulatory liabilities. CAPITALIZATION AND LIABILITIES Liabilities And Stockholders Equity [Abstract] Capitalization Capitalization Longterm Debt And Equity [Abstract] Common stock ($0.01 par value, 500,000 shares authorized, 179,921 shares outstanding at March 31 and 179,462 at December 31) Common Stock Value Paid-in-capital Additional Paid In Capital Common Stock Accumulated deficit Retained Earnings Accumulated Deficit Accumulated other comprehensive loss Accumulated Other Comprehensive Income Loss Net Of Tax Treasury stock Treasury Stock Value Total common stockholders' equity Stockholders Equity Including Portion Attributable To Noncontrolling Interest Long-term debt Long Term Debt And Capital Lease Obligations Redeemable preferred stock at redemption value Redeemable Preferred Stock At Redemption Value Total capitalization Capitalization Longterm Debt And Equity Current liabilities Liabilities Current [Abstract] Short-term debt Short Term Borrowings Current portion of long-term debt Long Term Debt And Capital Lease Obligations Current Accounts payable Accounts Payable Current Taxes accrued Taxes Payable Current Interest accrued Interest Payable Current Other Other Liabilities Current Total current liabilities Liabilities Current Regulatory and other long-term liabilities Deferred Credits And Regulatory Liabilities [Abstract] Advances for construction Customer Advances For Construction Deferred income taxes Deferred Tax Liabilities Noncurrent Deferred investment tax credits Accumulated Deferred Investment Tax Credit Regulatory liabilities Regulatory Liability Noncurrent Accrued pension expense Defined Benefit Pension Plan Liabilities Noncurrent Accrued postretirement benefit expense Other Postretirement Defined Benefit Plan Liabilities Noncurrent Other Other Liabilities Noncurrent Total regulatory and other long-term liabilities Deferred Credits And Regulatory Liabilities Contributions in aid of construction Contributions In Aid Of Construction Commitments and contingencies (See Note 9) Commitments And Contingencies TOTAL CAPITALIZATION AND LIABILITIES Liabilities And Stockholders Equity Common stock, par value Common Stock Par Or Stated Value Per Share Common stock, shares authorized Common Stock Shares Authorized Common stock, shares outstanding Common Stock Shares Outstanding Depreciation and amortization continuing operations. Loss (Gain) on sale of assets continuing operations. Income Statement [Abstract] Statement [Table] Statement [Table] Valuation Allowances and Reserves Type Valuation Allowances And Reserves Type [Axis] Valuation Allowances and Reserves Valuation Allowances And Reserves [Domain] Other funds. Other Funds Other Funds [Member] Borrowed funds. Borrowed Funds Borrowed Funds [Member] Statement [Line Items] Statement [Line Items] Operating revenues Revenues Operating expenses Operating Expenses [Abstract] Operation and maintenance Utilities Operating Expense Maintenance And Operations Depreciation and amortization Depreciation And Amortization Continuing Operations General taxes Taxes Excluding Income And Excise Taxes Gain on asset dispositions and purchases Gain Loss On Sale Of Assets Continuing Operations Total operating expenses, net Operating Expenses Operating income Operating Income Loss Other income (expenses) Nonoperating Income Expense [Abstract] Interest, net Interest Expense Allowance for funds used during construction Public Utilities Allowance For Funds Used During Construction Additions Amortization of debt expense Amortization Of Financing Costs Other, net Other Nonoperating Income Expense Total other income (expenses) Nonoperating Income Expense Income from continuing operations before income taxes Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments Provision for income taxes Income Tax Expense Benefit Income from continuing operations Income Loss From Continuing Operations Loss from discontinued operations, net of tax Income Loss From Discontinued Operations Net Of Tax Net income Net Income Loss Other comprehensive income (loss), net of tax: Other Comprehensive Income Loss Net Of Tax Period Increase Decrease [Abstract] Pension amortized to periodic benefit cost: Other Comprehensive Income Defined Benefit Plans Adjustment Net Of Tax Period Increase Decrease [Abstract] Prior service cost, net of tax of $25 and $27, respectively Other Comprehensive Income Loss Amortization Adjustment From A O C I Pension And Other Postretirement Benefit Plans For Net Prior Service Cost Credit Net Of Tax Actuarial (gain) loss, net of tax of $832 and $(5), respectively Other Comprehensive Income Loss Reclassification Adjustment From A O C I Pension And Other Postretirement Benefit Plans For Net Gain Loss Net Of Tax Foreign currency translation adjustment Other Comprehensive Income Loss Foreign Currency Transaction And Translation Adjustment Net Of Tax Unrealized loss on cash flow hedge, net of tax of $10 Other Comprehensive Income Unrealized Gain Loss On Derivatives Arising During Period Net Of Tax Other comprehensive income (loss) Other Comprehensive Income Loss Net Of Tax Comprehensive income Comprehensive Income Net Of Tax Basic earnings per share: Earnings Per Share Basic [Abstract] Income from continuing operations Income Loss From Continuing Operations Per Basic Share Loss from discontinued operations, net of tax Income Loss From Discontinued Operations Net Of Tax Per Basic Share Net income Earnings Per Share Basic Diluted earnings per share: Earnings Per Share Diluted [Abstract] Income from continuing operations Income Loss From Continuing Operations Per Diluted Share Loss from discontinued operations, net of tax Income Loss From Discontinued Operations Net Of Tax Per Diluted Share Net income Earnings Per Share Diluted Average common shares outstanding during the period Weighted Average Number Of Shares Outstanding Diluted Disclosure Items [Abstract] Basic Weighted Average Number Of Shares Outstanding Basic Diluted Weighted Average Number Of Diluted Shares Outstanding Dividends declared per common share Common Stock Dividends Per Share Declared Prior service cost, tax Other Comprehensive Income Loss Amortization Adjustment From A O C I Pension And Other Postretirement Benefit Plans For Net Prior Service Cost Credit Tax Actuarial (gain) loss, tax Other Comprehensive Income Loss Reclassification Adjustment From A O C I Pension And Other Postretirement Benefit Plans For Net Gain Loss Tax Unrealized loss on cash flow hedge, tax Other Comprehensive Income Unrealized Gain Loss On Derivatives Arising During Period Tax Payments to acquire property, plant and equipment of continuing operations. Cash flow non cash investing disclosure abstract.. Cash flow non cash financing activities disclosure. Statement Of Cash Flows [Abstract] CASH FLOWS FROM OPERATING ACTIVITIES Net Cash Provided By Used In Operating Activities [Abstract] Net income Adjustments Adjustments To Reconcile Net Income Loss To Cash Provided By Used In Operating Activities [Abstract] Depreciation and amortization Depreciation Depletion And Amortization Provision for deferred income taxes Deferred Income Tax Expense Benefit Amortization of deferred investment tax credits Deferred Income Taxes And Tax Credits Provision for losses on accounts receivable Provision For Doubtful Accounts Allowance for other funds used during construction Gain on asset dispositions and purchases Gains Losses On Sales Of Assets Pension and non-pension postretirement benefits Pension And Other Postretirement Benefit Expense Stock-based compensation expense Share Based Compensation Other, net Other Operating Activities Cash Flow Statement Changes in assets and liabilities Increase Decrease In Operating Capital [Abstract] Receivables and unbilled revenues Increase Decrease In Receivables Taxes receivable, including income taxes Increase Decrease In Income Taxes Receivable Other current assets Increase Decrease In Other Current Assets Pension and non-pension postretirement benefit contributions Pension And Other Postretirement Benefit Contributions Accounts payable Increase Decrease In Accounts Payable Taxes accrued, including income taxes Increase Decrease In Accrued Taxes Payable Interest accrued Increase Decrease In Interest Payable Net Change in book overdraft Increase Decrease In Outstanding Checks Operating Activities Other current liabilities Increase Decrease In Other Current Liabilities Net cash provided by 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 Of Continuing Operations Acquisitions Payments To Acquire Businesses Net Of Cash Acquired Proceeds from sale of assets Proceeds From Sale Of Productive Assets Removal costs from property, plant and equipment retirements, net Payments For Proceeds From Removal Costs Net funds released Increase Decrease In Restricted Cash Net cash used in investing activities Net Cash Provided By Used In Investing Activities CASH FLOWS FROM FINANCING ACTIVITIES Net Cash Provided By Used In Financing Activities [Abstract] Repayment of long-term debt Repayments Of Long Term Debt Proceeds from short-term borrowings with maturities greater than three months Proceeds From Short Term Debt Maturing In More Than Three Months Repayment of short-term borrowings with maturities greater than three months Repayments Of Debt Maturing In More Than Three Months Net short-term borrowings with maturities less than three months Proceeds From Repayments Of Short Term Debt Maturing In Three Months Or Less Proceeds from issuances of employee stock plans and DRIP Proceeds From Issuance Of Shares Under Incentive And Share Based Compensation Plans Including Stock Options Advances and contributions for construction, net of refunds of $4,146 and $5,277 at March 31, 2015 and 2014, respectively Proceeds From Construction Loans Payable Redemption of preferred stock Payments For Repurchase Of Preferred Stock And Preference Stock Dividends paid Payments Of Dividends Common Stock Tax benefit realized from equity compensation Excess Tax Benefit From Share Based Compensation Financing Activities Net cash provided by (used in) financing activities Net Cash Provided By Used In Financing Activities Net increase 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 end of period Non-cash investing activity: Cash Flow Non Cash Investing Disclosure [Abstract] Capital expenditures acquired on account but unpaid at end of period Capital Expenditures Incurred But Not Yet Paid Non-cash financing activity: Cash Flow Noncash Financing Activities Disclosure [Abstract] Advances and contributions Contribution Of Property Advances and contributions for construction, refunds Repayments Of Construction Loans Payable Statement Of Stockholders Equity [Abstract] Equity Components Statement Equity Components [Axis] Equity Component Equity Component [Domain] Common Stock Common Stock [Member] Paid-in Capital Additional Paid In Capital [Member] Accumulated Deficit Retained Earnings [Member] Accumulated Other Comprehensive Loss Accumulated Other Comprehensive Income [Member] Treasury Stock Treasury Stock [Member] Beginning Balance Beginning Balance (in shares) Shares Outstanding Cumulative effect of change in accounting principle Cumulative Effect Of Prospective Application Of New Accounting Principle Direct stock reinvestment and purchase plan, net of expense Stock Issued During Period Value Dividend Reinvestment Plan Direct stock reinvestment and purchase plan, net of expense (in shares) Stock Issued During Period Shares Dividend Reinvestment Plan Employee stock purchase plan Stock Issued During Period Value Employee Stock Purchase Plan Employee stock purchase plan (in shares) Stock Issued During Period Shares Employee Stock Purchase Plans Stock-based compensation activity Stock Issued During Period Value Share Based Compensation Stock-based compensation activity (in shares) Stock Issued During Period Shares Share Based Compensation Other comprehensive income (loss), net of tax Dividends Dividends Cash Ending Balance Ending Balance (in shares) Plan Name Plan Name [Axis] Plan Name Plan Name [Domain] Drip accounts. DRIP Accounts Drip Accounts [Member] Stock issuance expense Adjustments To Additional Paid In Capital Stock Issued Issuance Costs Other comprehensive income (loss), tax Other Comprehensive Income Loss Tax Organization Consolidation And Presentation Of Financial Statements [Abstract] Basis of Presentation Organization Consolidation And Presentation Of Financial Statements Disclosure [Text Block] New Accounting Pronouncements And Changes In Accounting Principles [Abstract] New Accounting Pronouncements New Accounting Pronouncements And Changes In Accounting Principles [Text Block] Discontinued Operations And Disposal Groups [Abstract] Divestitures Disposal Groups Including Discontinued Operations Disclosure [Text Block] Equity [Abstract] Stockholders' Equity Stockholders Equity Note Disclosure [Text Block] Debt Disclosure [Abstract] Long-Term Debt Long Term Debt [Text Block] Short Term Borrowings [Abstract] Short-Term Debt Short Term Debt [Text Block] Income Tax Disclosure [Abstract] Income Taxes Income Tax Disclosure [Text Block] Compensation And Retirement Disclosure [Abstract] Pension and Other Postretirement Benefits Pension And Other Postretirement Benefits Disclosure [Text Block] Commitments And Contingencies Disclosure [Abstract] Commitments and Contingencies Commitments And Contingencies Disclosure [Text Block] Environmental Remediation Obligations [Abstract] Environmental Matters Environmental Loss Contingency Disclosure [Text Block] Earnings Per Share [Abstract] Earnings Per Common Share Earnings Per Share [Text Block] Fair Value Disclosures [Abstract] Fair Value of Financial Assets and Liabilities Fair Value Disclosures [Text Block] Segment Reporting [Abstract] Segment Information Segment Reporting Disclosure [Text Block] Subsequent Events [Abstract] Subsequent Event Subsequent Events [Text Block] New Accounting Pronouncements New Accounting Pronouncements Policy Policy [Text Block] Summary of Discontinued Operations Presented in Consolidated Statements of Operations and Comprehensive Income Schedule Of Disposal Groups Including Discontinued Operations Income Statement Balance Sheet And Additional Disclosures [Text Block] Schedule Of Share Based Compensation Arrangements By Share Based Payment Award [Table] Schedule Of Share Based Compensation Arrangements By Share Based Payment Award [Table] Award Type Award Type [Axis] Equity Award Share Based Compensation Arrangements By Share Based Payment Award Award Type And Plan Name [Domain] Stock Options Employee Stock Option [Member] Restricted Stock Units Restricted Stock Units R S U [Member] Share Based Compensation Arrangement By Share Based Payment Award [Line Items] Share Based Compensation Arrangement By Share Based Payment Award [Line Items] Schedule of Accumulated Other Comprehensive Loss Schedule Of Accumulated Other Comprehensive Income Loss Table [Text Block] Weighted Average Assumptions Schedule Of Share Based Payment Award Stock Options Valuation Assumptions Table [Text Block] Summary of Stock Option Activity Schedule Of Share Based Compensation Stock Options Activity Table [Text Block] Additional Information to Stock Options Activity Schedule Of Cash Proceeds Received From Share Based Payment Awards Table [Text Block] Schedule of Weighted Average Assumptions Used. Weighted-Average Assumptions used in Monte Carlo Simulation and Weighted-Average Grant Date Fair Value of Restricted Stock Units Granted Schedule Of Weighted Average Assumptions Used Table [Text Block] Summary of Restricted Stock Unit Activity Schedule Of Share Based Compensation Restricted Stock Units Award Activity Table [Text Block] Long-Term Debt Retired Through Sinking Fund Payments Debt Instrument Redemption Table [Text Block] Balance Sheet Classification Schedule Of Fair Value Hedging Instruments Statements Of Financial Performance And Financial Position Location Table [Text Block] Income Statement Classification Schedule Of Derivative Instruments Gain Loss In Statement Of Financial Performance [Text Block] Schedule of Effective Tax Rates. Actual Effective Tax Rates on Continuing Operations Schedule Of Effective Tax Rate Table [Text Block] Components of Net Periodic Benefit Costs Schedule Of Net Benefit Costs Table [Text Block] Reconciliation Income (Loss) from Continuing Operations, (Loss) from Discontinued Operations and Net Income (Loss) and Weighted Average Common Shares Outstanding for Calculating Basic Net Earnings (Loss) Per Share Schedule Of Earnings Per Share Basic By Common Class [Text Block] Reconciliation of Income (Loss) from Continuing Operations, (Loss) from Discontinued Operations and Net Income (Loss) and Weighted Average Common Shares Outstanding for Calculating Diluted Earnings (Loss) Per Share Schedule Of Earnings Per Share Diluted By Common Class [Text Block] Potentially Dilutive Common Stock Equivalents Were Not Included in Earnings (Loss) Per Share Calculations Because They Were Anti-Dilutive Schedule Of Antidilutive Securities Excluded From Computation Of Earnings Per Share [Text Block] Carrying Amounts and Fair Values of Financial Instruments Fair Value By Balance Sheet Grouping [Text Block] Fair Value Measurements of Assets and Liabilities on Recurring Basis Schedule Of Fair Value Assets And Liabilities Measured On Recurring Basis Table [Text Block] Summarized Segment Information Schedule Of Segment Reporting Information By Segment [Text Block] Accounting Policies [Abstract] Recognized cumulative effect adjustment Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Table] Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Table] Disposal Group Name Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Axis] Disposal Groups, Including Discontinued Operations, Name Disposal Groups Including Discontinued Operations Name [Domain] Terratec environmental limited. Terratec Environmental Limited Terratec Environmental Limited [Member] Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items] Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items] Operating revenues Disposal Group Including Discontinued Operation Revenue Total operating expenses, net Disposal Group Including Discontinued Operation Operating Expense Loss from discontinued operations before income taxes Discontinued Operation Income Loss From Discontinued Operation Before Income Tax Benefit from income taxes Discontinued Operation Tax Effect Of Discontinued Operation Loss from discontinued operations Accumulated Other Comprehensive Income Loss [Table] Accumulated Other Comprehensive Income Loss [Table] Employee Benefit Plan Funded Status Accumulated Defined Benefit Plans Adjustment Net Transition Asset Obligation [Member] Amortization of Prior Service Cost Accumulated Defined Benefit Plans Adjustment Net Prior Service Cost Credit [Member] Amortization of Actuarial (Gain) Loss Accumulated Defined Benefit Plans Adjustment Net Unamortized Gain Loss [Member] Foreign Currency Translation Accumulated Translation Adjustment [Member] Loss on Cash Flow Hedge Accumulated Net Gain Loss From Designated Or Qualifying Cash Flow Hedges [Member] Accumulated Other Comprehensive Income Loss [Line Items] Accumulated Other Comprehensive Income Loss [Line Items] Accumulated other comprehensive income (loss) Beginning balance Other comprehensive income (loss) before reclassifications Other Comprehensive Income Loss Before Reclassifications Net Of Tax Amounts reclassified from accumulated other comprehensive income (loss) Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax Accumulated other comprehensive income (loss) Ending balance Stockholders equity note. Stockholders equity note. Stockholders Equity Note [Table] Stockholders Equity Note [Table] Range Range [Axis] Range Range [Member] Minimum Minimum [Member] Maximum Maximum [Member] Stockholders Equity Note [Line Items] Stockholders Equity Note [Line Items] Vesting period Share Based Compensation Arrangement By Share Based Payment Award Award Vesting Period1 Disclosure Of Compensation Related Costs Sharebased Payments [Abstract] Dividend yield Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Expected Dividend Rate Expected volatility Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Expected Volatility Rate Risk-free interest rate Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Risk Free Interest Rate Expected life (years) Sharebased Compensation Arrangement By Sharebased Payment Award Fair Value Assumptions Expected Term1 Exercise price Sharebased Compensation Shares Authorized Under Stock Option Plans Exercise Price Range Exercisable Options Weighted Average Exercise Price1 Grant date fair value per share Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Weighted Average Grant Date Fair Value Maximum terms Sharebased Compensation Arrangement By Sharebased Payment Award Expiration Period Unrecognized compensation cost Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized Weighted-average period (in years) Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized Period For Recognition1 Options outstanding at January 1, 2015 Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number Granted Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Forfeited or expired Share Based Compensation Arrangement By Share Based Payment Award Options Forfeitures And Expirations In Period Exercised Stock Issued During Period Shares Stock Options Exercised Options outstanding at March 31, 2015 Exercisable at March 31, 2015 Share Based Compensation Arrangement By Share Based Payment Award Options Exercisable Number Weighted Average Exercise Price (per share), Options outstanding at January 1, 2015 Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price Weighted Average Exercise Price (per share), Granted Share Based Compensation Arrangements By Share Based Payment Award Options Grants In Period Weighted Average Exercise Price Weighted Average Exercise Price (per share), Forfeited or expired Share Based Compensation Arrangement By Share Based Payment Award Options Forfeitures And Expirations In Period Weighted Average Exercise Price Weighted Average Exercise Price (per share), Exercised Share Based Compensation Arrangements By Share Based Payment Award Options Exercises In Period Weighted Average Exercise Price Weighted Average Exercise Price (per share), Options outstanding at March 31, 2015 Weighted Average Exercise Price (per share), Options outstanding at March 31, 2015 Share Based Compensation Arrangement By Share Based Payment Award Options Exercisable Weighted Average Exercise Price Weighted Average Remaining Life (years), Options outstanding at March 31, 2015 Sharebased Compensation Arrangement By Sharebased Payment Award Options Outstanding Weighted Average Remaining Contractual Term2 Weighted Average Remaining Life (years), Exercisable at March 31, 2015 Sharebased Compensation Arrangement By Sharebased Payment Award Options Exercisable Weighted Average Remaining Contractual Term1 Aggregate intrinsic Value, Options outstanding at March 31, 2015 Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Intrinsic Value Aggregate intrinsic Value, Exercisable at March 31, 2015 Sharebased Compensation Arrangement By Sharebased Payment Award Options Exercisable Intrinsic Value1 Intrinsic value Share Based Compensation Arrangement By Share Based Payment Award Options Exercises In Period Total Intrinsic Value Exercise proceeds Proceeds From Stock Options Exercised Income tax benefit Employee Service Share Based Compensation Tax Benefit Realized From Exercise Of Stock Options Key terms of the grants. Number of grants Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period Restricted shares granted Restricted Shares Granted Share based compensation arrangement by share based payment award fair value assumptions grant date fair value per share. Grant date fair value per share Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Grant Date Fair Value Per Share Share based compensation arrangement by share based payment award equity instruments other than options performance share adjustment in period. Non-vested total at January 1, 2015 Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Number Granted Performance share adjustment Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Performance Share Adjustment In Period Vested Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period Forfeited Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Forfeited In Period Non-vested total at March 31, 2015 Share based compensation arrangement by share based payment award equity instruments other than options performance share adjustment. Weighted-average grant date fair value (per share), non-vested total beginning balance Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Weighted Average Grant Date Fair Value Weighted-average grant date fair value (per share), granted Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period Weighted Average Grant Date Fair Value Weighted-average grant date fair value (per share), Performance share adjustment Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Performance Share Adjustment Weighted-average grant date fair value (per share), vested Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period Weighted Average Grant Date Fair Value Weighted-average grant date fair value (per share), forfeited Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Forfeitures Weighted Average Grant Date Fair Value Weighted-average grant date fair value (per share), non-vested total ending balance Intrinsic value Sharebased Compensation Arrangement By Sharebased Payment Award Equity Instruments Other Than Options Aggregate Intrinsic Value Vested Income tax benefit Employee Service Share Based Compensation Tax Benefit From Compensation Expense Accrued dividend equivalents Dividends Share Based Compensation Cash Debt instrument maturity range start. Debt instrument maturity range end. Debt Instrument [Table] Debt Instrument [Table] Debt Instrument, Redemption, Period Debt Instrument Redemption Period [Axis] Debt Instrument, Redemption, Period Debt Instrument Redemption Period [Domain] Debt retired in current period. Debt retired during the year Debt Retired In Current Period [Member] Debt Instrument Debt Instrument [Axis] Debt Instrument, Name Debt Instrument Name [Domain] Fixed rate two. Fixed rate two Fixed Rate Two [Member] Legal Entity Legal Entity [Axis] Entity Entity [Domain] American Water Capital Corp AWCC. American Water Capital Corp. ("AWCC") American Water Capital Corp Awcc [Member] Other subsidiaries Subsidiaries [Member] Long-term Debt, Type Longterm Debt Type [Axis] Long-term Debt, Type Longterm Debt Type [Domain] Private activity bonds and government funded debt. Private activity bonds and government funded debt Private Activity Bonds And Government Funded Debt [Member] Capital lease payments Capital lease payments Capital Lease Payments [Member] Schedule of Financial Instruments Subject to Mandatory Redemption by Settlement Terms Schedule Of Shares Subject To Mandatory Redemption By Settlement Terms [Axis] Financial Instruments Subject to Mandatory Redemption, Financial Instrument Shares Subject To Mandatory Redemption Financial Instrument [Domain] Mandatorily redeemable preferred stock Mandatorily Redeemable Preferred Stock [Member] Debt Instrument [Line Items] Debt Instrument [Line Items] Interest Rate Debt Instrument Interest Rate Stated Percentage Interest Rate, Minimum Debt Instrument Interest Rate Stated Percentage Rate Range Minimum Interest Rate, Maximum Debt Instrument Interest Rate Stated Percentage Rate Range Maximum Maturity Date, Minimum Debt Instrument Maturity Range Start Maturity Date, Maximum Debt Instrument Maturity Range End Total retirements and redemptions Repayments Of Debt Total retirements and redemptions Repayments Of Debt And Capital Lease Obligations Total retirements and redemptions Derivative Instrument Derivative Instrument Risk [Axis] Derivative Contract Derivative Contract Type [Domain] Interest Rate Swap Interest Rate Swap [Member] Variable Rate Variable Rate [Axis] Variable Rate Variable Rate [Domain] London Interbank Offered Rate (LIBOR) [Member] London Interbank Offered Rate L I B O R [Member] Senior notes six point zero eight five percent. 6.085% Senior Notes Senior Notes Six Point Zero Eight Five Percent [Member] Fixed rate debt Derivative Notional Amount Derivative description of variable rate basis Debt Instrument Description Of Variable Rate Basis Debt, basis spread on variable rate Debt Instrument Basis Spread On Variable Rate1 Derivative Instruments And Hedging Activities Disclosure [Abstract] Derivative [Table] Derivative [Table] Credit Derivatives Contract Type Credit Derivatives By Contract Type [Axis] Credit Derivatives Contract Type Credit Derivatives Contract Type [Domain] Other Other Credit Derivatives [Member] Derivative [Line Items] Derivative [Line Items] Regulatory and other long-term assets Derivative Fair Value Of Derivative Asset Interest rate swap fair value adjustment Derivative Instruments In Hedges At Fair Value Net Derivative Instruments Gain Loss By Hedging Relationship By Income Statement Location By Derivative Instrument Risk [Table] Derivative Instruments Gain Loss By Hedging Relationship By Income Statement Location By Derivative Instrument Risk [Table] Income Statement Location Income Statement Location [Axis] Income Statement Location Income Statement Location [Domain] Net interest Net Interest Net Interest [Member] Hedging Designation Hedging Designation [Axis] Hedging Designation Hedging Designation [Domain] Designated as Hedging Instrument Designated As Hedging Instrument [Member] Derivative Instruments Gain Loss [Line Items] Derivative Instruments Gain Loss [Line Items] Gain (loss) on swap Change In Unrealized Gain Loss On Fair Value Hedging Instruments1 Gain (loss) on borrowing Change In Unrealized Gain Loss On Hedged Item In Fair Value Hedge1 Hedge ineffectiveness Gain Loss On Fair Value Hedge Ineffectiveness Net Schedule Of Short Term Debt [Table] Schedule Of Short Term Debt [Table] Credit Facility Credit Facility [Axis] Credit Facility Credit Facility [Domain] Commercial Paper Commercial Paper [Member] Short Term Debt [Line Items] Short Term Debt [Line Items] Commercial paper, discount Debt Instrument Unamortized Discount Estimated effective income tax rate. Estimated Effective Income Tax Rate Estimated Effective Income Tax Rate Actual effective tax rate Effective Income Tax Rate Continuing Operations Schedule Of Defined Benefit Plans Disclosures [Table] Schedule Of Defined Benefit Plans Disclosures [Table] Defined Benefit Plans and Other Postretirement Benefit Plans Defined Benefit Plans Disclosures Defined Benefit Plans [Axis] Defined Benefit Plan and Other Postretirement Benefit Plan Defined Benefit Plans [Domain] Pension Plan Asset Pension Plans Defined Benefit [Member] Other Postretirement Benefit Cost Other Postretirement Benefit Plans Defined Benefit [Member] Defined Benefit Plan Disclosure [Line Items] Defined Benefit Plan Disclosure [Line Items] Service cost Defined Benefit Plan Service Cost Interest cost Defined Benefit Plan Interest Cost Expected return on plan assets Defined Benefit Plan Expected Return On Plan Assets Prior service cost Defined Benefit Plan Amortization Of Prior Service Cost Credit Actuarial (gain) loss Defined Benefit Plan Amortization Of Gains Losses Net periodic pension benefit cost Defined Benefit Plan Net Periodic Benefit Cost Other Postretirement Benefits Company contributions Defined Benefit Plan Contributions By Employer Expected contributions during the balance of 2015 Defined Benefit Plans Estimated Future Employer Contributions In Current Fiscal Year Loss contingency, probable loss Loss Contingency Accrual At Carrying Value Loss contingency, range of reasonably possible loss, maximum Loss Contingency Range Of Possible Loss Maximum Site Contingency [Table] Site Contingency [Table] Environmental Remediation Contingency Environmental Remediation Contingency [Axis] Environmental Remediation Contingency Environmental Remediation Contingency [Domain] National oceanic and atmospheric administration. NOAA National Oceanic And Atmospheric Administration [Member] Site Contingency [Line Items] Site Contingency [Line Items] Remediation costs accrued Accrual For Environmental Loss Contingencies Accrual for environmental loss contingencies payments Accrual For Environmental Loss Contingencies Payments Regulatory assets Regulatory Assets Undistributed earnings allocated to common shareholders. Income (Loss) from Continuing Operations Available to Common Stockholders, Basic Income from continuing operations Less: Distributed earnings to common shareholders Dividends Less: Distributed earnings to participating securities Dividends And Interest Paid Undistributed earnings Undistributed Earnings Undistributed earnings allocated to common shareholders Undistributed Earnings Allocated To Common Shareholders Undistributed earnings allocated to participating securities Undistributed Earnings Loss Allocated To Participating Securities Basic Total income from continuing operations available to common shareholders, basic Income Loss From Continuing Operations Available To Common Stockholders Basic Total income available to common shareholders, basic Net Income Loss Available To Common Stockholders Basic Weighted-average common shares outstanding, basic Income (Loss) from Continuing Operations Available to Common Stockholders, Diluted Schedule Of Earnings Per Share Diluted By Common Class [Table] Schedule Of Earnings Per Share Diluted By Common Class [Table] Employee stock purchase plan. Employee Stock Purchase Plan Employee Stock Purchase Plan [Member] Earnings Per Share Diluted [Line Items] Earnings Per Share Diluted [Line Items] Total income available to common shareholders, basic Undistributed earnings for participating securities Undistributed Earnings Loss Allocated To Participating Securities Diluted Total income from continuing operations available to common shareholders, diluted Income Loss From Continuing Operations Available To Common Stockholders Diluted Total income available to common shareholders, diluted Net Income Loss Available To Common Stockholders Diluted Common stock equivalents Incremental Common Shares Attributable To Share Based Payment Arrangements Weighted-average common shares outstanding, diluted Schedule Of Antidilutive Securities Excluded From Computation Of Earnings Per Share [Table] Schedule Of Antidilutive Securities Excluded From Computation Of Earnings Per Share [Table] Antidilutive Securities Antidilutive Securities Excluded From Computation Of Earnings Per Share By Antidilutive Securities [Axis] Antidilutive Securities, Name Antidilutive Securities Name [Domain] Stock Options Stock Option [Member] Restricted Stock Units Performance Conditions Not Met Restricted Stock [Member] Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items] Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items] Potentially dilutive common stock equivalents not included in the earnings per share calculations Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount Preferred stocks with mandatory redemption requirements carrying amount. Long term debt (excluding capital lease obligations) carrying amount. Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Table] Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Table] Fair Value, Hierarchy Fair Value By Fair Value Hierarchy Level [Axis] Fair Value Hierarchy Fair Value Measurements Fair Value Hierarchy [Domain] Level 1 Fair Value Inputs Level1 [Member] Level 2 Fair Value Inputs Level2 [Member] Level 3 Fair Value Inputs Level3 [Member] Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] Preferred stock with mandatory redemption Requirements, carrying amount Preferred Stocks With Mandatory Redemption Requirements Carrying Amount Long-term debt (excluding capital lease obligations), carrying amount Long Term Debt Excluding Capital Lease Obligations Carrying Amount Preferred stock with mandatory redemption Requirements, fair value Mandatorily Redeemable Preferred Stock Fair Value Disclosure Long-term debt (excluding capital lease obligations), fair value Long Term Debt Fair Value Rabbi trust investments. Restricted funds Restricted Cash And Cash Equivalents Rabbi trust investments Rabbi Trust Investments Deposits Deposit Assets Mark-to-market derivative asset Total assets Assets Fair Value Disclosure Deferred compensation obligation Fair Value Liabilities Measured On Recurring Basis Obligations Mark-to-market derivative liability Derivative Fair Value Of Derivative Liability Total liabilities Liabilities Fair Value Disclosure Total net assets (liabilities) Assets Net Restricted investments Restricted Investments Number of Operating Segments Number Of Operating Segments Number of Reportable Segments Number Of Reportable Segments Schedule Of Segment Reporting Information By Segment [Table] Schedule Of Segment Reporting Information By Segment [Table] Consolidation Items Consolidation Items [Axis] Consolidation Items Consolidation Items [Domain] Operating Segments Operating Segments [Member] Other Corporate Non Segment [Member] Segments Statement Business Segments [Axis] Segments Segment [Domain] Regulated business. Regulated Businesses Regulated Business [Member] Market based operations. Market-Based Operations Market Based Operations [Member] Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Net operating revenues Total operating expenses, net Income from continuing operations before income taxes Subsequent Event [Table] Subsequent Event [Table] Subsequent Event Type Subsequent Event Type [Axis] Subsequent Event Type Subsequent Event Type [Domain] Subsequent Event Subsequent Event [Member] Subsequent Event [Line Items] Subsequent Event [Line Items] Recovery of prior expenditures incurred Loss Contingency Related Receivable Carrying Value Receipts