Document and Entity Information [Abstract] Document and Entity Information Statement [Table] Statement [Line Items] Document Type Amendment Flag Document Period End Date Document Fiscal Year Focus Document Fiscal Period Focus Entity Registrant Name Entity Central Index Key Current Fiscal Year End Date Entity Filer Category Entity Common Stock, Shares Outstanding Consolidated Balance Sheets ASSETS Property, plant and equipment Utility plant-at original cost, net of accumulated depreciation of $3,402,466 in 2010 and $3,168,078 in 2009 Utility plant-at original cost, net of accumulated depreciation of $3,229,600 at March 31 and $3,182,944 at December 31 Public Utilities, Property, Plant and Equipment, Net, Total Tangible assets that are held by an entity for use other than utility production; net of accumulated depreciation. Non Utility Property Net Nonutility property, net of accumulated depreciation of $153,032 at March 31 and $143,051 at December 31 Total property, plant and equipment Property, Plant and Equipment, Net, Ending Balance Property, Plant and Equipment, Net, Beginning Balance Total property, plant and equipment Current assets Cash and cash equivalents Cash Equivalents, at Carrying Value, Total Restricted Cash and Cash Equivalents, Current Restricted funds Utility customer accounts receivable Allowance for doubtful accounts receivable current Allowance for uncollectible accounts Allowance for Doubtful Accounts Receivable, Current, Ending Balance Allowance for Doubtful Accounts Receivable, Current, Beginning Balance Allowance for uncollectible accounts Unbilled utility revenues Receivable net current Other receivables, net Receivables, Net, Current, Total Non-Regulated trade and other receivables, net Income taxes receivable Materials and supplies Inventory, Raw Materials and Supplies, Total Assets of Disposal Group, Including Discontinued Operation, Current Assets of Disposal Group, Including Discontinued Operation, Current, Total Assets of discontinued operations Other Assets, Current Other Total current assets Total current assets Deferred Charges, Regulatory Assets, and Other Assets, Noncurrent [Abstract] Deferred Charges Regulatory Assets And Other Assets Noncurrent Abstract Regulatory and other long-term assets Regulatory Assets Noncurrent Regulatory assets Restricted Cash and Cash Equivalents, Noncurrent Restricted funds Goodwill, noncurrent Total net, ending balance Total net, beginning balance Total goodwill Goodwill Other Assets, Noncurrent Other Assets, Noncurrent, Total Other Deferred Charges, Regulatory Assets, and Other Assets, Noncurrent Deferred Charges Regulatory Assets And Other Assets Noncurrent Total regulatory and other long-term assets Total regulatory and other long-term assets TOTAL ASSETS Total assets TOTAL ASSETS CAPITALIZATION AND LIABILITIES Capitalization Common stock ($.01 par value, 500,000 shares authorized, 174,996 shares outstanding in 2010 and 174,630 in 2009) Common Stock, Value, Issued, Ending Balance Common Stock, Value, Issued, Beginning Balance Common stock ($.01 par value, 500,000 shares authorized, 175,347 and 174,996 shares outstanding at March 31 and December 31, respectively) Common Stock, Value, Issued, Total Paid-in capital Additional Paid in Capital, Common Stock, Ending Balance Additional Paid in Capital, Common Stock, Beginning Balance Paid-in-capital Retained Earnings (Accumulated Deficit) Retained Earnings (Accumulated Deficit), Ending Balance Retained Earnings (Accumulated Deficit), Beginning Balance Retained Earnings (Accumulated Deficit), Total Accumulated deficit Accumulated Other Comprehensive Income (Loss), Net of Tax Accumulated Other Comprehensive Income (Loss), Net of Tax, Ending Balance Accumulated Other Comprehensive Income (Loss), Net of Tax, Beginning Balance Accumulated Other Comprehensive Income (Loss), Net of Tax, Total Accumulated other comprehensive loss Treasury stock Treasury stock Treasury Stock, Value, Ending Balance Treasury Stock, Value, Beginning Balance Total of all Common Shareholders' Equity (deficit) items. Common Shareholders Equity Common Stockholders Equity Common stockholders' equity Preferred Stock Value Preferred Stock, Value, Issued, Ending Balance Preferred Stock, Value, Issued, Beginning Balance Preferred stock without mandatory redemption requirements Preferred Stock, Value, Issued, Total Total stockholders' equity Balance Balance Total stockholders' equity Long-term Debt, Excluding Current Maturities [Abstract] Long-term debt Long-term Debt, Excluding Current Maturities Long-term Debt, Excluding Current Maturities, Total Long-term debt Redeemable preferred stock at redemption value Total capitalization Total capitalization Current liabilities Short-term Borrowings Short-term Borrowings, Total Short-term debt Current portion of long-term debt Long-term Debt, Current Maturities, Total Accounts Payable, Current Accounts Payable, Current, Total Accounts payable Taxes accrued, including income taxes of $906 in 2010 and $1,777 in 2009 Taxes accrued, including income taxes of $0 at March 31 and December 31 Taxes Payable, Current, Total Interest Payable, Current Interest accrued Liabilities of Disposal Group, Including Discontinued Operation, Current Liabilities of Disposal Group, Including Discontinued Operation, Current, Total Liabilities of discontinued operations Other Liabilities, Current Other Liabilities, Current, Total Other Total current liabilities Total current liabilities Deferred Credits and Regulatory Liabilities [Abstract] Deferred Credits And Regulatory Liabilities Abstract Regulatory and other long-term liabilities Advances for construction Deferred income taxes Deferred investment tax credits Regulatory liabilities Regulatory Liability, Noncurrent, Total Accrued pension expense Accrued postretirement benefit expense Other Liabilities, Noncurrent Other Liabilities, Noncurrent, Total Other Deferred Credits and Regulatory Liabilities Deferred Credits And Regulatory Liabilities Total Regulatory And Other Long-term Liabilities Total regulatory and other long-term liabilities Contributions in aid of construction Commitments and contingencies (See Note 16) Commitments and contingencies (See Note 9) TOTAL CAPITALIZATION AND LIABILITIES TOTAL CAPITALIZATION AND LIABILITIES Utility plant, accumulated depreciation Nonutility property, accumulated depreciation Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment, Ending Balance Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment, Beginning Balance Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment, Total Common stock, par value Common stock, shares authorized Common stock, shares outstanding Common Stock, Shares, Outstanding, Ending Balance Common Stock, Shares, Outstanding, Beginning Balance Taxes accrued, income taxes Consolidated Statements of Operations and Comprehensive Income Operating revenues Net operating revenues Revenues, Total Operating expenses Operation and maintenance Depreciation and amortization Depreciation, Depletion and Amortization, Total Taxes Excluding Income and Excise Taxes General taxes Taxes, Miscellaneous, Total (Gain) loss on sale of assets Loss (gain) on sale of assets Loss (gain) on sale of assets Gains (Losses) on Sales of Assets, Total (Gain) loss on sale of assets Total operating expenses, net Total operating expenses, net Total operating expenses, net Operating Income (Loss) Operating income Other income (expenses) Interest, net Interest, net Interest Expense, Total Allowance for other funds used during construction Allowance for other funds used during construction Allowance for borrowed funds used during construction Allowance for borrowed funds used during construction Amortization of debt expense Amortization of debt expense Other Nonoperating Income (Expense) Other Nonoperating Income (Expense), Total Other, net Total other income (deductions) Total other income (expenses) Income (loss) before income taxes Income (Loss) before income taxes Income from continuing operations before income taxes Provision for income taxes Income Tax Expense (Benefit), Total Income (Loss) from Continuing Operations Attributable to Parent Income from continuing operations Income from continuing operations Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest Income from discontinued operations, net of tax Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest, Total Net income (loss) Net income Net income Net income (loss) Pension plan amortized to periodic benefit cost: Prior service cost, net of tax of $50, $29 and $17, respectively Prior service cost, net of tax of $28 and $12, respectively Prior service cost, net of tax of $xx and $12, respectively Actuarial loss, net of tax of $2,793, $3,832 and $0, respectively Actuarial loss, net of tax of $2,793, $3,832 and $0, respectively Actuarial loss, net of tax of $720 and $698, respectively Foreign currency translation adjustment Foreign currency translation adjustment Other Comprehensive Income, Foreign Currency Transaction and Translation Adjustment, Net of Tax, Total Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Other comprehensive income Other comprehensive income Total comprehensive income (loss) Comprehensive income Earnings Per Share, Basic [Abstract] Basic earnings per common share: Income (Loss) from Continuing Operations, Per Basic Share Income from continuing operations Income (Loss) from Continuing Operations, Per Outstanding Share, Total Income (Loss) from Discontinued Operations, Net of Tax, Per Basic Share Income from discontinued operations, net of tax Income (Loss) from Discontinued Operations, Net of Tax, Per Outstanding Share, Total Earnings Per Share, Basic Basic net income (loss) per common share Net income Basic Earnings Per Share, Diluted [Abstract] Diluted earnings per common share: Income (Loss) from Continuing Operations, Per Diluted Share Income from continuing operations Income (Loss) from Discontinued Operations, Net of Tax, Per Diluted Share Income (loss) from discontinued operations, net of tax Income (Loss) from Discontinued Operations, Net of Tax, Per Diluted Share, Total Income from discontinued operations, net of tax Earnings Per Share, Diluted Diluted net income (loss) per commons share Net income Diluted Average common shares outstanding during the period: Weighted Average Number of Shares Outstanding, Basic Weighted average common shares outstanding, basic Weighted Average Number of Shares Outstanding, Basic, Total Basic Weighted Average Number of Shares Outstanding, Diluted Weighted average common shares outstanding, diluted Weighted Average Number of Shares Outstanding, Diluted, Total Diluted Dividends per common share Prior service cost, tax Actuarial loss, tax Consolidated Statements of Cash Flows CASH FLOWS FROM OPERATING ACTIVITIES Adjustments Provision for deferred income taxes Deferred Income Tax Expense (Benefit), Total Amortization of deferred investment tax credits Provision for losses on utility accounts receivable Pension and non-pension post retirement benefits Pension and Other Postretirement Benefit Expense, Total Adjustments, Noncash Items, to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities, Other Other, net Changes in assets and liabilities Receivables and unbilled utility revenues Receivables and unbilled utility revenues Increase (Decrease) in Receivables, Total Increase (Decrease) in Income Taxes Receivable Income taxes receivable Other current assets Other current assets Increase (Decrease) in Prepaid, Deferred Expense and Other Assets, Total Pension and non-pension post retirement benefit contributions Pension and non-pension post retirement benefit contributions Pension and Other Postretirement Benefit Contributions, Total Increase (Decrease) in Accounts Payable Increase (Decrease) in Accounts Payable, Total Accounts payable Taxes accrued, including income taxes Increase (Decrease) in Interest Payable, Net Interest accrued Other current liabilities Increase (Decrease) in Accrued Liabilities, Total Net cash provided by operating activities Net cash provided by operating activities CASH FLOWS FROM INVESTING ACTIVITIES Construction expenditures Capital expenditures Capital expenditures Payments to Acquire Property, Plant, and Equipment, Total Acquisitions Acquisitions Payments to Acquire Businesses, Net of Cash Acquired, Total Proceeds from sale of assets and securities Proceeds from Sale of Productive Assets, Total Removal costs from property, plant and equipment retirements, net Removal costs from property, plant and equipment retirements, net Net restricted funds released (invested) Net funds released Increase (Decrease) in Restricted Cash, Total Net cash used in investing activities Net cash used in investing activities CASH FLOWS FROM FINANCING ACTIVITIES Proceeds from long-term debt Proceeds from Issuance of Long-term Debt, Total Proceeds from issuance Repayment of long-term debt Repayment of long-term debt Repayments of Long-term Debt, Total Net borrowings (repayments) under short-term debt agreements Net borrowings under short-term debt agreements Proceeds from (Repayments of) Short-term Debt, Total Proceeds from employee stock plan issuances and DRIP Proceeds from employee stock plan issuances Proceeds from Issuance of Shares under Incentive and Share-based Compensation Plans, Including Stock Options, Total Advances and contributions for construction, net of refunds of $35,830 in 2010, $27,481 in 2009 and $57,580 in 2008 Advances and contributions for construction, net of refunds of $4,072 and $11,941 at March 31, 2011 and 2010 Change in bank overdraft position Debt issuance costs Debt issuance costs Redemption of preferred stock Redemption of preferred stocks Payments Of Dividends Dividends paid Payments of Dividends, Total Net cash provided by financing activities Net cash provided by (used in) financing activities Net decrease in cash and cash equivalents Net increase (decrease) in cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Cash and cash equivalents at end of period Cash and cash equivalents at beginning of period Cash and Cash Equivalents, at Carrying Value, Total Cash Flow, Noncash Investing Disclosure [Abstract] Cash Flow Noncash Investing Disclosure Abstract Non-cash investing activity: Capital expenditures acquired on account but unpaid as of year-end Capital expenditures acquired on account but unpaid at quarter-end Cash Flow, Noncash Financing Activities Disclosure [Abstract] Cash Flow Noncash Financing Activities Disclosure Abstract Non-cash financing activity: Advances and contributions Advances and contributions for construction, refunds Consolidated Statement of Changes in Stockholders' Equity Statement, Equity Components [Axis] Equity Component [Domain] Common Stock [Member] Paid-in Capital [Member] Accumulated Deficit [Member] Accumulated Other Comprehensive Loss [Member] Treasury Stock [Member] Preferred Stock of Subsidiary Companies Without Mandatory Redemption Requirements [Member] Number of shares of stock held by shareholders. Shares, Outstanding Balance (in shares) Balance (in shares) Stock Issued During Period, Value, Dividend Reinvestment Plan Direct stock reinvestment and purchase plan (DRIP), net of expense Stock Issued During Period, Shares, Dividend Reinvestment Plan Direct stock reinvestment and purchase plan (DRIP), net of expense (in shares) Stock Issued During Period, Value, Employee Stock Purchase Plan Employee stock purchase plan (ESPP) Stock Issued During Period, Shares, Employee Stock Purchase Plans Employee stock purchase plan (ESPP) (in shares) Stock-based compensation, employee stock purchase plan Stock-based compensation activity Stock-based compensation activity Stock-based compensation activity (in shares) Preferred stock redemption Preferred stock redemption Redeemable Preferred Stock Increase (Decrease) in Carrying Amount, Total Other comprehensive income (loss), net of tax Other comprehensive income, net of tax of $748 Other Comprehensive Income (Loss), Net of Tax, Total Other comprehensive income, net of tax Dividends, Cash Dividends Dividends, Cash, Total Common stock offering, expenses Expenses associated with issuance of stock Direct stock reinvestment and purchase plan (DRIP), expense Other comprehensive income (loss), tax Other comprehensive income (loss), tax Other Comprehensive Income (Loss), Tax, Total Organization, Consolidation and Presentation of Financial Statements [Abstract] Basis of Presentation Organization Consolidation And Presentation Of Financial Statements Disclosure [Text Block] Organization and Operation Basis of Presentation New Accounting Pronouncements New Accounting Pronouncements And Changes In Accounting Principles [Text Block] New Accounting Pronouncements Goodwill and Intangible Assets Disclosure [Abstract] Goodwill Schedule of Goodwill [Text Block] Summary of Changes in Goodwill Goodwill Stockholders' Equity Stockholders Equity Note Disclosure Text Block Stockholders' Equity Long-Term Debt Long-term Debt [Text Block] Long-Term Debt Long-Term Debt Short-Term Debt Short-term Debt [Text Block] Short-Term Debt Income Taxes