2.2.0.25falsefalse004010 - Statement - CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY ParentheticaltruefalseIn Thousandsfalse1falsefalseUSDfalsefalse1/1/2010 - 12/31/2010 USD ($) USD ($) / shares $c00024http://www.sec.gov/CIK0000741508duration2010-01-01T00:00:002010-12-31T00:00:00u000Standardhttp://www.xbrl.org/2003/iso4217USDiso42170u002Dividehttp://www.xbrl.org/2003/iso4217USDiso4217http://www.xbrl.org/2003/instancesharesxbrli0u001Standardhttp://www.xbrl.org/2003/instancesharesxbrli0USDUSD$2falsefalseUSDfalsefalse1/1/2009 - 12/31/2009 USD ($) USD ($) / shares $c00009http://www.sec.gov/CIK0000741508duration2009-01-01T00:00:002009-12-31T00:00:00u000Standardhttp://www.xbrl.org/2003/iso4217USDiso42170u001Standardhttp://www.xbrl.org/2003/instancesharesxbrli0u002Dividehttp://www.xbrl.org/2003/iso4217USDiso4217http://www.xbrl.org/2003/instancesharesxbrli0USDUSD$3falsefalseUSDfalsefalse1/1/2008 - 12/31/2008 USD ($) USD ($) / shares $c00004http://www.sec.gov/CIK0000741508duration2008-01-01T00:00:002008-12-31T00:00:00u000Standardhttp://www.xbrl.org/2003/iso4217USDiso42170u002Dividehttp://www.xbrl.org/2003/iso4217USDiso4217http://www.xbrl.org/2003/instancesharesxbrli0u001Standardhttp://www.xbrl.org/2003/instancesharesxbrli0USDUSD$2true0nve_ConsolidatedStatementsOfCommonStockholdersEquityParentheticalAbstractnvefalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringNo definition available.falsefalseCONSOLIDATED STATEMENTS OF COMMON STOCKHOLDERS' EQUITY - Parenthetical [Abstract]3false0us-gaap_OtherComprehensiveIncomeCumulativeEffectOfChangeInAccountingPrincipleTaxesus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalselabel1truefalsefalse00falsetruefalsefalsefalse2truefalsefalse00falsetruefalsefalsefalse3truefalsefalse25140002514falsetruefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe sum of income taxes on the cumulative effects of a change in accounting principle recognized in a period as other comprehensive income.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 154 -Paragraph 9, 17 falsefalseCompensation retirement benefits (net of taxes ($2,514)4false0us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansTaxus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse217000217falsetruefalsefalsefalse2truefalsefalse7200072falsetruefalsefalsefalse3truefalsefalse284000284falsetruefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryTax effects of the net changes to accumulated comprehensive income during the period related to benefit plans.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph c(3) Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 25 falsefalseChange in compensation retirement benefits liability and amortization (Net of taxes $217, $72, and $284 in 2010, 2009, and 2008, respectively33CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY Parenthetical (USD $)ThousandsUnKnownUnKnownUnKnownfalsetrue