2.4.0.8155 - Disclosure - STOCK BASED COMPENSATION (Details Textual)truefalsefalse1false falsefalseP01_01_2013To06_30_2013http://www.sec.gov/CIK0001493552duration2013-01-01T00:00:002013-06-30T00:00:00pureStandardhttp://www.xbrl.org/2003/instancepurexbrli01true 3us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItemsus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalselabel1falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Share-based Compensation Arrangement by Share-based Payment Award [Line Items]2false 4us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestExercisableWeightedAverageRemainingContractualTerm1us-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse006 yearsfalsefalsefalsexbrli:durationItemTypenaWeighted average remaining contractual term for fully vested and expected to vest options that are exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (e)(2) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 false0Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Weighted Average Remaining Contractual Term3false 4nvsl_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExpiredWeightedAverageRemainingContractualTerm1nvsl_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse0010 yearsfalsefalsefalsexbrli:durationItemTypenaRepresents the stock options are expired weighted average remaining contractual term.No definition available.false0Share Based Compensation Arrangement By Share Based Payment Award Options Expired Weighted Average Remaining Contractual Term14false 4nvsl_StockOptionsAndRestrictedStockAwardsPercentageForWithinOneYearnvsl_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truetruefalse00falsefalsefalsenum:percentItemTypepureRepresents the stock option vested percentage within one year.No definition available.false0Stock Options and Restricted Stock Awards Percentage For Within One Year5false 4nvsl_StockOptionsAndRestrictedStockAwardsPercentageForTwoThroughSixYearsnvsl_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truetruefalse0.20.2falsefalsefalsenum:percentItemTypepureRepresents the stock option vested percentage within two through six years.No definition available.false0Stock Options and Restricted Stock Awards Percentage For Two Through Six YearsfalseSTOCK BASED COMPENSATION (Details Textual)UnKnownUnKnownUnKnownUnKnowntruefalsefalseSheethttp://www.nvsl.com/role/StockBasedCompensationDetailsTextual15