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Significant Accounting Policies (Concentration of Credit Risk) (Details) (USD $)
In Thousands, unless otherwise specified
Mar. 31, 2015
Dec. 31, 2014
Mar. 31, 2014
Dec. 31, 2013
Concentration Risk [Line Items]        
Cash $ 7,108us-gaap_CashAndCashEquivalentsAtCarryingValue $ 6,426us-gaap_CashAndCashEquivalentsAtCarryingValue $ 6,739us-gaap_CashAndCashEquivalentsAtCarryingValue $ 4,987us-gaap_CashAndCashEquivalentsAtCarryingValue
Policy receivables and agents' balances, net 11,285us-gaap_PremiumsAndOtherReceivablesNet 10,948us-gaap_PremiumsAndOtherReceivablesNet    
Uninsured Deposit Risk [Member]        
Concentration Risk [Line Items]        
Cash 3,924us-gaap_CashAndCashEquivalentsAtCarryingValue
/ us-gaap_ConcentrationRiskByTypeAxis
= nsec_UninsuredDepositRiskMember
     
Single Largest Agent Balance Due [Member]        
Concentration Risk [Line Items]        
Policy receivables and agents' balances, net $ 937us-gaap_PremiumsAndOtherReceivablesNet
/ us-gaap_ConcentrationRiskByTypeAxis
= nsec_SingleLargestAgentBalanceDueMember