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Reclassification adjustments include: (1) the unrealized holding gain or loss, net of tax, at the date of the transfer for a debt security from the held-to-maturity category transferred into the available-for-sale category. Also includes the unrealized gain or loss at the date of transfer for a debt security from the available-for-sale category transferred into the held-to-maturity category; (2) the unrealized gains or losses realized upon the sale of securities, after tax; and (3) the unrealized gains or losses realized upon the write-down of securities, after tax.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 17, 22 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 13 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph c(3) Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 24 -Subparagraph b falsefalseChange in net unrealized gains on securities16false0navg_NonCreditOtherThanTemporaryImpairmentGainsLossesNetOfTaxChangeInPeriodnavgfalsecreditdurationNon-credit other-than-temporary impairment gains (losses), net of tax, change in period.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1falsefalsefalse00falsefalsefalsetruefalse2falsefalsefalse00falsefalsefalsetruefalse3falsefalsefalse00falsefalsefalsetruefalse4falsefalsefalse00falsefalsefalsetruefalse5falsefalsefalse00falsefalsefalsetruefalse6truefalsefalse-273000-273falsefalsefalsetruefalse7falsefalsefalse00falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryNon-credit other-than-temporary impairment gains (losses), net of tax, change in period.No authoritative reference available.falsefalseChange in net non-credit other-than-temporary impairment losses17false0us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentNetOfTaxPeriodIncreaseDecreaseus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1falsefalsefalse00falsefalsefalsetruefalse2falsefalsefalse00falsefalsefalsetruefalse3falsefalsefalse00falsefalsefalsetruefalse4falsefalsefalse00falsefalsefalsetruefalse5falsefalsefalse00falsefalsefalsetruefalse6truefalsefalse931000931falsefalsefalsetruefalse7truefalsefalse931000931falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryAdjustment that results from the process of translating subsidiary financial statements and foreign equity investments into functional currency of the reporting entity, net of tax.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 52 -Paragraph 13, 20, 31 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 24 -Subparagraph b Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 14, 17, 19, 26 falsefalseChange in net cumulative translation adjustments18false0us-gaap_StockholdersEquityus-gaaptruecreditinstantNo definition available.falsefalsefalsetruefalsefalsefalsefalsetruefalseperiodendlabelinstant2011-03-31T00:00:000001-01-01T00:00:001truefalsefalse00falsetruefalsetruefalse2truefalsefalse18290001829falsetruefalsetruefalse3truefalsefalse318281000318281falsetruefalsetruefalse4truefalsefalse-77987000-77987falsetruefalsetruefalse5truefalsefalse531619000531619falsetruefalsetruefalse6truefalsefalse4143000041430falsetruefalsetruefalse7truefalsefalse815172000815172falsetruefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryTotal of all Stockholders' Equity (deficit) items, net of receivables from officers, directors owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). 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 A3 -Appendix A Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 4 -Section E Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 29, 30, 31 -Article 5 falsefalseBalance at end of period at Mar. 31, 2011718Consolidated Statements of Stockholders' Equity (Unaudited) (USD $)ThousandsUnKnownUnKnownUnKnownfalsetrue