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Does not include common shares that have been repurchased.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 12 -Paragraph 10 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Article 3 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 30 -Article 5 falsefalseBalance, Shares at Dec. 31, 20073false0us-gaap_ProfitLossus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse00falsefalsefalsetruefalse2truefalsefalse00falsefalsefalsetruefalse3truefalsefalse208887000208887falsefalsefalsetruefalse4truefalsefalse00falsefalsefalsetruefalse5truefalsefalse208887000208887falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph A1, A4, A5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 5 -Subparagraph b Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 29 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph a Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph c(1) falsefalseNet Income4false0nve_StockIssuedDuringPeriodValueDividendReinvestmentPlanAndEmployeeStockPurchasePlannvefalsecreditdurationRepresents the aggregate change in value for stock issued during the period as a result of employee stock purchase plan and...falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse578000578falsefalsefalsetruefalse2truefalsefalse96720009672falsefalsefalsetruefalse3truefalsefalse00falsefalsefalsetruefalse4truefalsefalse00falsefalsefalsetruefalse5truefalsefalse1025000010250falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryRepresents the aggregate change in value for stock issued during the period as a result of employee stock purchase plan and the value of stock issued during the period from a dividend reinvestment plan (DRIP). 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Also includes any direct costs associated with stock issues under a shelf registration.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Technical Practice Aid (TPA) -Number 4110 -Paragraph 1, 10 falsefalseCommon Stock issuance costs7false0us-gaap_AdjustmentsToAdditionalPaidInCapitalTaxEffectFromShareBasedCompensationus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalselabel1truefalsefalse00falsefalsefalsetruefalse2truefalsefalse365000365falsefalsefalsetruefalse3truefalsefalse00falsefalsefalsetruefalse4truefalsefalse00falsefalsefalsetruefalse5truefalsefalse365000365falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryTax benefit associated with any share-based compensation plan other than an employee stock ownership plan (ESOP). 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A dividend reinvestment plan allows the holder of the stock to reinvest dividends paid to them by the entity on new issues of stock by the entity.No authoritative reference available.falsefalseDividend Reinvestment and Employee Benefits, Amount16false0nve_StockIssuedDuringPeriodSharesDividendReinvestmentPlanAndEmployeeStockPurchasePlanSharesnvefalsenadurationNumber of shares issued during the period as a result of an employee stock purchase plan and the number of shares issued...falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse517340517340falsefalsefalsetruefalse2falsefalsefalse00falsefalsefalsetruefalse3falsefalsefalse00falsefalsefalsetruefalse4falsefalsefalse00falsefalsefalsetruefalse5falsefalsefalse00falsefalsefalsefalsefalseSharesxbrli:sharesItemTypesharesNumber of shares issued during the period as a result of an employee stock purchase plan and the number of shares issued during the period from a dividend reinvestment plan (DRIP). 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This element includes paid and unpaid dividends declared during the period.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Article 3 falsefalseDividends Declared21false0us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestus-gaaptruecreditinstantNo definition available.falsefalsefalsetruefalsefalsefalsefalsetruefalseperiodendlabelinstant2009-12-31T00:00:000001-01-01T00:00:001truefalsefalse234834000234834falsefalsefalsetruefalse2truefalsefalse27003290002700329falsefalsefalsetruefalse3truefalsefalse295247000295247falsefalsefalsetruefalse4truefalsefalse-6488000-6488falsefalsefalsetruefalse5truefalsefalse32239220003223922falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryTotal of Stockholders' Equity (deficit) items, net of receivables from officers, directors owners, and affiliates of the entity including portions attributable to both the parent and noncontrolling interests (previously referred to as minority interest), if any. 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A dividend reinvestment plan allows the holder of the stock to reinvest dividends paid to them by the entity on new issues of stock by the entity.No authoritative reference available.falsefalseDividend Reinvestment and Employee Benefits (in shares)26false0us-gaap_AdjustmentsToAdditionalPaidInCapitalStockIssuedIssuanceCostsus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalselabel1truefalsefalse00falsefalsefalsetruefalse2truefalsefalse-27000-27falsefalsefalsetruefalse3truefalsefalse00falsefalsefalsetruefalse4truefalsefalse00falsefalsefalsetruefalse5truefalsefalse-27000-27falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryDirect costs (e.g., legal and accounting fees) associated with issuing stock that is deducted from additional paid in capital. Also includes any direct costs associated with stock issues under a shelf registration.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Technical Practice Aid (TPA) -Number 4110 -Paragraph 1, 10 falsefalseCommon Stock issuance costs27false0us-gaap_AdjustmentsToAdditionalPaidInCapitalTaxEffectFromShareBasedCompensationus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalselabel1truefalsefalse00falsefalsefalsetruefalse2truefalsefalse3200032falsefalsefalsetruefalse3truefalsefalse00falsefalsefalsetruefalse4truefalsefalse00falsefalsefalsetruefalse5truefalsefalse3200032falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryTax benefit associated with any share-based compensation plan other than an employee stock ownership plan (ESOP). The tax benefit results from the deduction by the entity on its tax return for an award of stock that exceeds the cumulative compensation cost for common stock or preferred stock recognized for financial reporting. Includes any resulting tax benefit that exceeds the previously recognized deferred tax asset (excess tax benefits).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 123R -Paragraph 62 falsefalseTax benefit from stock options exercised28false0us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPeriodIncreaseDecreaseus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse00falsefalsefalsetruefalse2truefalsefalse00falsefalsefalsetruefalse3truefalsefalse00falsefalsefalsetruefalse4truefalsefalse-403000-403falsefalsefalsetruefalse5truefalsefalse-403000-403falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryNet changes to accumulated comprehensive income during the period related to benefit plans, after tax.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 158 -Paragraph 7 -Subparagraph c Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph c(3) Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 14, 17, 22, 26 falsefalseChange in compensation retirement benefits liability and amortization29false0us-gaap_DividendsCommonStockCashus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalselabel1truefalsefalse00falsefalsefalsetruefalse2truefalsefalse00falsefalsefalsetruefalse3truefalsefalse-105799000-105799falsefalsefalsetruefalse4truefalsefalse00falsefalsefalsetruefalse5truefalsefalse-105799000-105799falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryCommon stock cash dividend declared by an entity during the period. This element includes paid and unpaid dividends declared during the period.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Article 3 falsefalseDividends Declared31false0us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestus-gaaptruecreditinstantNo definition available.falsefalsefalsetruefalsefalsefalsefalsetruefalseperiodendlabelinstant2010-12-31T00:00:000001-01-01T00:00:001truefalsefalse235323000235323falsetruefalsetruefalse2truefalsefalse27059540002705954falsetruefalsetruefalse3truefalsefalse416432000416432falsetruefalsetruefalse4truefalsefalse-6891000-6891falsetruefalsetruefalse5truefalsefalse33508180003350818falsetruefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryTotal of Stockholders' Equity (deficit) items, net of receivables from officers, directors owners, and affiliates of the entity including portions attributable to both the parent and noncontrolling interests (previously referred to as minority interest), if any. The entity including portions attributable to the parent and noncontrolling interests is sometimes referred to as the economic entity. This excludes temporary equity and is sometimes called permanent equity.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 25 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 26 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph A3 -Appendix A falsefalseBalance, Amount at Dec. 31, 201032false0us-gaap_CommonStockSharesOutstandingus-gaaptruenainstantNo definition available.falsefalsefalsetruefalsefalsefalsefalsetruefalseperiodendlabelinstant2010-12-31T00:00:000001-01-01T00:00:001truefalsefalse235322553235322553falsefalsefalsetruefalse2falsefalsefalse00falsefalsefalsetruefalse3falsefalsefalse00falsefalsefalsetruefalse4falsefalsefalse00falsefalsefalsetruefalse5falsefalsefalse00falsefalsefalsefalsefalseSharesxbrli:sharesItemTypesharesTotal number of shares of common stock held by shareholders. May be all or portion of the number of common shares authorized. These shares represent the ownership interest of the common shareholders. Excludes common shares repurchased by the entity and held as Treasury shares. Shares outstanding equals shares issued minus shares held in treasury. Does not include common shares that have been repurchased.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 12 -Paragraph 10 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Article 3 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 30 -Article 5 falsefalseBalance, Shares at Dec. 31, 2010529CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (USD $)ThousandsNoRoundingUnKnownUnKnownfalsetrue