2.4.0.8135 - Disclosure - INVESTMENT SECURITIES (Details 1)truefalseIn Thousands, unless otherwise specifiedfalse1false USDfalsefalse$P01_01_2013To06_30_2013http://www.sec.gov/CIK0001493552duration2013-01-01T00:00:002013-06-30T00:00:00USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170pureStandardhttp://www.xbrl.org/2003/instancepurexbrli0USDUSD$2false USDfalsefalse$P01_01_2012To12_31_2012http://www.sec.gov/CIK0001493552duration2012-01-01T00:00:002012-12-31T00:00:00USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170pureStandardhttp://www.xbrl.org/2003/instancepurexbrli0USDUSD$1true 3nvsl_UnrealizedLossOnInvestmentsLineItemsnvsl_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalselabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Unrealized Loss on Investments [Line Items]2false 4nvsl_HeldToMaturitySecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerNumberOfSecuritiesnvsl_falsenainstantfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse66falsefalsefalse2truefalsefalse66falsefalsefalsexbrli:integerItemTypeintegerThis item contains disclosure of the number of securities for 12 months or more in the held-to-maturity investments determined to be temporarily impaired.No definition available.false0Securities in Continuous Unrealized Loss Position 12 or More Consecutive Months, Number of Securities3false 4us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValueus-gaap_truedebitinstantfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse69940006994USD$falsetruefalse2truefalsefalse75100007510USD$falsetruefalsexbrli:monetaryItemTypemonetaryThis item represents the fair value of securities categorized as held-to-maturity securities that have been in a continuous unrealized loss position for twelve months or longer.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27337-111563 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 6 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27290-111563 false2Securities in Continuous Unrealized Loss Position 12 or More Consecutive Months, Fair Market Value4false 4us-gaap_HeldtomaturitySecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAggregateLossus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-991000-991USD$falsefalsefalse2truefalsefalse-504000-504USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of unrealized loss on investments in held-to-maturity securities that have been in a loss position for twelve months or longer.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27337-111563 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 6 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27290-111563 false2Securities in Continuous Unrealized Loss Position 12 or More Consecutive Months, Unrealized Loss5false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3false USDtruefalse$P01_01_2013To06_30_2013_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMemberusgaapMajorTypesOfDebtAndEquitySecuritiesAxishttp://www.sec.gov/CIK0001493552duration2013-01-01T00:00:002013-06-30T00:00:00falsefalseMortgage-backed Securities, Issued by Private Enterprises [Member]us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMemberus-gaap_MajorTypesOfDebtAndEquitySecuritiesAxisexplicitMemberUSDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170pureStandardhttp://www.xbrl.org/2003/instancepurexbrli0USDUSD$nanafalse0Mortgage-backed Securities, Issued by Private Enterprises [Member]6true 3nvsl_UnrealizedLossOnInvestmentsLineItemsnvsl_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalselabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Unrealized Loss on Investments [Line Items]7false 4nvsl_HeldToMaturitySecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerNumberOfSecuritiesnvsl_falsenainstantfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse11falsefalsefalse2truefalsefalse11falsefalsefalsexbrli:integerItemTypeintegerThis item contains disclosure of the number of securities for 12 months or more in the held-to-maturity investments determined to be temporarily impaired.No definition available.false0Securities in Continuous Unrealized Loss Position 12 or More Consecutive Months, Number of Securities8false 4us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValueus-gaap_truedebitinstantfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse276000276USD$falsefalsefalse2truefalsefalse294000294USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThis item represents the fair value of securities categorized as held-to-maturity securities that have been in a continuous unrealized loss position for twelve months or longer.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27337-111563 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 6 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27290-111563 false2Securities in Continuous Unrealized Loss Position 12 or More Consecutive Months, Fair Market Value9false 4us-gaap_HeldtomaturitySecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAggregateLossus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-9000-9USD$falsefalsefalse2truefalsefalse-20000-20USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of unrealized loss on investments in held-to-maturity securities that have been in a loss position for twelve months or longer.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27337-111563 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 6 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27290-111563 false2Securities in Continuous Unrealized Loss Position 12 or More Consecutive Months, Unrealized Loss10false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse5false USDtruefalse$P01_01_2013To06_30_2013_AuctionRateTrustPreferredSecuritiesMemberusgaapMajorTypesOfDebtAndEquitySecuritiesAxishttp://www.sec.gov/CIK0001493552duration2013-01-01T00:00:002013-06-30T00:00:00falsefalseAuction-Rate Trust Preferred Securities [Member]us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxisxbrldihttp://xbrl.org/2006/xbrldinvsl_AuctionRateTrustPreferredSecuritiesMemberus-gaap_MajorTypesOfDebtAndEquitySecuritiesAxisexplicitMemberUSDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170pureStandardhttp://www.xbrl.org/2003/instancepurexbrli0USDUSD$nanafalse0Auction-Rate Trust Preferred Securities [Member]11true 3nvsl_UnrealizedLossOnInvestmentsLineItemsnvsl_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalselabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Unrealized Loss on Investments [Line Items]12false 4nvsl_HeldToMaturitySecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerNumberOfSecuritiesnvsl_falsenainstantfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse55falsefalsefalse2truefalsefalse55falsefalsefalsexbrli:integerItemTypeintegerThis item contains disclosure of the number of securities for 12 months or more in the held-to-maturity investments determined to be temporarily impaired.No definition available.false0Securities in Continuous Unrealized Loss Position 12 or More Consecutive Months, Number of Securities13false 4us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValueus-gaap_truedebitinstantfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse67180006718USD$falsefalsefalse2truefalsefalse72160007216USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThis item represents the fair value of securities categorized as held-to-maturity securities that have been in a continuous unrealized loss position for twelve months or longer.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27337-111563 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 6 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27290-111563 false2Securities in Continuous Unrealized Loss Position 12 or More Consecutive Months, Fair Market Value14false 4us-gaap_HeldtomaturitySecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAggregateLossus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-982000-982USD$falsetruefalse2truefalsefalse-484000-484USD$falsetruefalsexbrli:monetaryItemTypemonetaryAmount of unrealized loss on investments in held-to-maturity securities that have been in a loss position for twelve months or longer.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27337-111563 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 6 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27290-111563 false2Securities in Continuous Unrealized Loss Position 12 or More Consecutive Months, Unrealized LossfalseINVESTMENT SECURITIES (Details 1) (USD $)ThousandsUnKnownUnKnownUnKnowntruefalsefalseSheethttp://www.nvsl.com/role/InvestmentSecuritiesDetails1214