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Fair Value Accounting - Significant Unobservable Inputs (Details) (Available-for-sale Securities [Member], Mortgage securities [Member], Present Value Analysis [Member], Fair Value, Inputs, Level 3 [Member])
 12 Months Ended
Dec. 31, 2014
Fair Value Inputs, Quantitative Information [Line Items]  
Fair value inputs, weighted average life, in years 2 years
Minimum [Member]
  
Fair Value Inputs, Quantitative Information [Line Items]  
Fair value inputs, prepayment rates 6.30%us-gaap_FairValueInputsPrepaymentRate
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InformationByCategoryOfDebtSecurityAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_ValuationTechniqueAxis
= novc_PresentValueAnalysisMember
Maximum [Member]
  
Fair Value Inputs, Quantitative Information [Line Items]  
Fair value inputs, prepayment rates 9.30%us-gaap_FairValueInputsPrepaymentRate
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InformationByCategoryOfDebtSecurityAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_ValuationTechniqueAxis
= novc_PresentValueAnalysisMember