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Significant Accounting Policies (Concentration of Credit Risk) (Details) (USD $)
In Thousands, unless otherwise specified
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Concentration Risk [Line Items]      
Cash $ 6,426us-gaap_CashAndCashEquivalentsAtCarryingValue $ 4,987us-gaap_CashAndCashEquivalentsAtCarryingValue $ 6,779us-gaap_CashAndCashEquivalentsAtCarryingValue
Policy receivables and agents' balances, net 10,948us-gaap_PremiumsAndOtherReceivablesNet 10,276us-gaap_PremiumsAndOtherReceivablesNet  
Uninsured Deposit Risk [Member]      
Concentration Risk [Line Items]      
Cash 2,878us-gaap_CashAndCashEquivalentsAtCarryingValue
/ us-gaap_ConcentrationRiskByTypeAxis
= nsec_UninsuredDepositRiskMember
   
Single Largest Agent Balance Due [Member]      
Concentration Risk [Line Items]      
Policy receivables and agents' balances, net $ 554us-gaap_PremiumsAndOtherReceivablesNet
/ us-gaap_ConcentrationRiskByTypeAxis
= nsec_SingleLargestAgentBalanceDueMember