<?xml version='1.0' encoding='UTF-8'?>
<FilingSummary>
  <Version>3.2.0.727</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>390</ContextCount>
  <ElementCount>320</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>true</FootnotesReported>
  <SegmentCount>93</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>6</UnitCount>
  <MyReports>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>0001000 - Document - Document and Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nationalwesternlife.com/role/DocumentAndEntityInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>1001000 - Statement - Condensed Consolidated Balance Sheets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nationalwesternlife.com/role/CondensedConsolidatedBalanceSheets</Role>
      <ShortName>Condensed Consolidated Balance Sheets</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>1001001 - Statement - Condensed Consolidated Balance Sheets (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nationalwesternlife.com/role/CondensedConsolidatedBalanceSheetsParenthetical</Role>
      <ShortName>Condensed Consolidated Balance Sheets (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>1002000 - Statement - Condensed Consolidated Statements of Earnings</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nationalwesternlife.com/role/CondensedConsolidatedStatementsOfEarnings</Role>
      <ShortName>Condensed Consolidated Statements of Earnings</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>1003000 - Statement - Condensed Consolidated Statements of Comprehensive Income</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nationalwesternlife.com/role/CondensedConsolidatedStatementsOfComprehensiveIncome</Role>
      <ShortName>Condensed Consolidated Statements of Comprehensive Income</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>1004000 - Statement - Condensed Consolidated Statements of Stockholders' Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nationalwesternlife.com/role/CondensedConsolidatedStatementsOfStockholdersEquity</Role>
      <ShortName>Condensed Consolidated Statements of Stockholders' Equity</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>1005000 - Statement - Condensed Consolidated Statements of Cash Flows</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nationalwesternlife.com/role/CondensedConsolidatedStatementsOfCashFlows</Role>
      <ShortName>Condensed Consolidated Statements of Cash Flows</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>2101100 - Disclosure - Consolidation and Basis of Presentation</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nationalwesternlife.com/role/ConsolidationAndBasisOfPresentation</Role>
      <ShortName>Consolidation and Basis of Presentation</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>2102100 - Disclosure - New Accounting Pronouncements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nationalwesternlife.com/role/NewAccountingPronouncements</Role>
      <ShortName>New Accounting Pronouncements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>2103100 - Disclosure - Stockholders' Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nationalwesternlife.com/role/StockholdersEquity</Role>
      <ShortName>Stockholders' Equity</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>2104100 - Disclosure - Earnings Per Share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nationalwesternlife.com/role/EarningsPerShare</Role>
      <ShortName>Earnings Per Share</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>2105100 - Disclosure - Pension and Other Postretirement Plans</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nationalwesternlife.com/role/PensionAndOtherPostretirementPlans</Role>
      <ShortName>Pension and Other Postretirement Plans</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>2106100 - Disclosure - Segment and Other Operating Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nationalwesternlife.com/role/SegmentAndOtherOperatingInformation</Role>
      <ShortName>Segment and Other Operating Information</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>2107100 - Disclosure - Share-Based Payments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nationalwesternlife.com/role/ShareBasedPayments</Role>
      <ShortName>Share-Based Payments</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>2108100 - Disclosure - Commitments and Contingencies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nationalwesternlife.com/role/CommitmentsAndContingencies</Role>
      <ShortName>Commitments and Contingencies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>2109100 - Disclosure - Investments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nationalwesternlife.com/role/Investments</Role>
      <ShortName>Investments</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>2110100 - Disclosure - Fair Values of Financial Instruments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nationalwesternlife.com/role/FairValuesOfFinancialInstruments</Role>
      <ShortName>Fair Values of Financial Instruments</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>2111100 - Disclosure - Derivative Investments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nationalwesternlife.com/role/DerivativeInvestments</Role>
      <ShortName>Derivative Investments</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>2301301 - Disclosure - Consolidation and Basis of Presentation (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nationalwesternlife.com/role/ConsolidationAndBasisOfPresentationTables</Role>
      <ShortName>Consolidation and Basis of Presentation (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.nationalwesternlife.com/role/ConsolidationAndBasisOfPresentation</ParentRole>
      <Position>19</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>2304301 - Disclosure - Earnings Per Share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nationalwesternlife.com/role/EarningsPerShareTables</Role>
      <ShortName>Earnings Per Share (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.nationalwesternlife.com/role/EarningsPerShare</ParentRole>
      <Position>20</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>2305301 - Disclosure - Pension and Other Postretirement Plans (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nationalwesternlife.com/role/PensionAndOtherPostretirementPlansTables</Role>
      <ShortName>Pension and Other Postretirement Plans (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.nationalwesternlife.com/role/PensionAndOtherPostretirementPlans</ParentRole>
      <Position>21</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>2306301 - Disclosure - Segment and Other Operating Information (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nationalwesternlife.com/role/SegmentAndOtherOperatingInformationTables</Role>
      <ShortName>Segment and Other Operating Information (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.nationalwesternlife.com/role/SegmentAndOtherOperatingInformation</ParentRole>
      <Position>22</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>2307301 - Disclosure - Share-Based Payments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nationalwesternlife.com/role/ShareBasedPaymentsTables</Role>
      <ShortName>Share-Based Payments (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.nationalwesternlife.com/role/ShareBasedPayments</ParentRole>
      <Position>23</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>2309301 - Disclosure - Investments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nationalwesternlife.com/role/InvestmentsTables</Role>
      <ShortName>Investments (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.nationalwesternlife.com/role/Investments</ParentRole>
      <Position>24</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>2310301 - Disclosure - Fair Value of Financial Instruments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nationalwesternlife.com/role/FairValueOfFinancialInstrumentsTables</Role>
      <ShortName>Fair Value of Financial Instruments (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <Position>25</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>2311301 - Disclosure - Derivative Investments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nationalwesternlife.com/role/DerivativeInvestmentsTables</Role>
      <ShortName>Derivative Investments (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.nationalwesternlife.com/role/DerivativeInvestments</ParentRole>
      <Position>26</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>2401402 - Disclosure - Consolidation and Basis of Presentation (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nationalwesternlife.com/role/ConsolidationAndBasisOfPresentationDetails</Role>
      <ShortName>Consolidation and Basis of Presentation (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.nationalwesternlife.com/role/ConsolidationAndBasisOfPresentationTables</ParentRole>
      <Position>27</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>2403401 - Disclosure - Stockholders' Equity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nationalwesternlife.com/role/StockholdersEquityDetails</Role>
      <ShortName>Stockholders' Equity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.nationalwesternlife.com/role/StockholdersEquity</ParentRole>
      <Position>28</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>2404402 - Disclosure - Earnings Per Share (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nationalwesternlife.com/role/EarningsPerShareDetails</Role>
      <ShortName>Earnings Per Share (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.nationalwesternlife.com/role/EarningsPerShareTables</ParentRole>
      <Position>29</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>2404403 - Disclosure - Earnings Per Share (Antidilutive Securities) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nationalwesternlife.com/role/EarningsPerShareAntidilutiveSecuritiesDetails</Role>
      <ShortName>Earnings Per Share (Antidilutive Securities) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.nationalwesternlife.com/role/EarningsPerShareTables</ParentRole>
      <Position>30</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>2405402 - Disclosure - Pension and Other Postretirement Plans (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nationalwesternlife.com/role/PensionAndOtherPostretirementPlansDetails</Role>
      <ShortName>Pension and Other Postretirement Plans (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.nationalwesternlife.com/role/PensionAndOtherPostretirementPlansTables</ParentRole>
      <Position>31</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>2406402 - Disclosure - Segment and Other Operating Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nationalwesternlife.com/role/SegmentAndOtherOperatingInformationDetails</Role>
      <ShortName>Segment and Other Operating Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.nationalwesternlife.com/role/SegmentAndOtherOperatingInformationTables</ParentRole>
      <Position>32</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>2407402 - Disclosure - Share-Based Payments (General Descriptions) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nationalwesternlife.com/role/ShareBasedPaymentsGeneralDescriptionsDetails</Role>
      <ShortName>Share-Based Payments (General Descriptions) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.nationalwesternlife.com/role/ShareBasedPaymentsTables</ParentRole>
      <Position>33</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>2407403 - Disclosure - Share-Based Payments (Options and Stock Appreciation Rights Outstanding) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nationalwesternlife.com/role/ShareBasedPaymentsOptionsAndStockAppreciationRightsOutstandingDetails</Role>
      <ShortName>Share-Based Payments (Options and Stock Appreciation Rights Outstanding) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.nationalwesternlife.com/role/ShareBasedPaymentsTables</ParentRole>
      <Position>34</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>2407404 - Disclosure - Share-Based Payments (Exercise Range) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nationalwesternlife.com/role/ShareBasedPaymentsExerciseRangeDetails</Role>
      <ShortName>Share-Based Payments (Exercise Range) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.nationalwesternlife.com/role/ShareBasedPaymentsTables</ParentRole>
      <Position>35</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>2407405 - Disclosure - Share-Based Payments (Black Scholes Option Pricing Model Assumptions) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nationalwesternlife.com/role/ShareBasedPaymentsBlackScholesOptionPricingModelAssumptionsDetails</Role>
      <ShortName>Share-Based Payments (Black Scholes Option Pricing Model Assumptions) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.nationalwesternlife.com/role/ShareBasedPaymentsTables</ParentRole>
      <Position>36</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>2408401 - Disclosure - Commitments and Contingencies (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nationalwesternlife.com/role/CommitmentsAndContingenciesDetails</Role>
      <ShortName>Commitments and Contingencies (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.nationalwesternlife.com/role/CommitmentsAndContingencies</ParentRole>
      <Position>37</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>2409402 - Disclosure - Investments (Investment Gains and Losses) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nationalwesternlife.com/role/InvestmentsInvestmentGainsAndLossesDetails</Role>
      <ShortName>Investments (Investment Gains and Losses) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.nationalwesternlife.com/role/InvestmentsTables</ParentRole>
      <Position>38</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>2409403 - Disclosure - Investments (Securities Held to Maturity) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nationalwesternlife.com/role/InvestmentsSecuritiesHeldToMaturityDetails</Role>
      <ShortName>Investments (Securities Held to Maturity) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.nationalwesternlife.com/role/InvestmentsTables</ParentRole>
      <Position>39</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>2409404 - Disclosure - Investments (Securities Available for Sale) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nationalwesternlife.com/role/InvestmentsSecuritiesAvailableForSaleDetails</Role>
      <ShortName>Investments (Securities Available for Sale) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.nationalwesternlife.com/role/InvestmentsTables</ParentRole>
      <Position>40</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>2409405 - Disclosure - Investments (Unrealized Losses) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nationalwesternlife.com/role/InvestmentsUnrealizedLossesDetails</Role>
      <ShortName>Investments (Unrealized Losses) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.nationalwesternlife.com/role/InvestmentsTables</ParentRole>
      <Position>41</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>2409406 - Disclosure - Investments (Mortgage Loans and Real Estate) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nationalwesternlife.com/role/InvestmentsMortgageLoansAndRealEstateDetails</Role>
      <ShortName>Investments (Mortgage Loans and Real Estate) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.nationalwesternlife.com/role/InvestmentsTables</ParentRole>
      <Position>42</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>2410402 - Disclosure - Fair Value of Financial Instruments (Assets and Liabilities Measured on Recurring Basis) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nationalwesternlife.com/role/FairValueOfFinancialInstrumentsAssetsAndLiabilitiesMeasuredOnRecurringBasisDetails</Role>
      <ShortName>Fair Value of Financial Instruments (Assets and Liabilities Measured on Recurring Basis) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.nationalwesternlife.com/role/FairValueOfFinancialInstrumentsTables</ParentRole>
      <Position>43</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>2410403 - Disclosure - Fair Value of Financial Instruments (Fair Value Measurements for Level 3 Instruments) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nationalwesternlife.com/role/FairValueOfFinancialInstrumentsFairValueMeasurementsForLevel3InstrumentsDetails</Role>
      <ShortName>Fair Value of Financial Instruments (Fair Value Measurements for Level 3 Instruments) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.nationalwesternlife.com/role/FairValueOfFinancialInstrumentsTables</ParentRole>
      <Position>44</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>2410404 - Disclosure - Fair Values of Financial Instruments (Fair Value by Balance Sheet Grouping) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nationalwesternlife.com/role/FairValuesOfFinancialInstrumentsFairValueByBalanceSheetGroupingDetails</Role>
      <ShortName>Fair Values of Financial Instruments (Fair Value by Balance Sheet Grouping) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.nationalwesternlife.com/role/FairValuesOfFinancialInstruments</ParentRole>
      <Position>45</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>2410405 - Disclosure - Fair Values of Financial Instruments (Quantitative Information) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nationalwesternlife.com/role/FairValuesOfFinancialInstrumentsQuantitativeInformationDetails</Role>
      <ShortName>Fair Values of Financial Instruments (Quantitative Information) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.nationalwesternlife.com/role/FairValuesOfFinancialInstruments</ParentRole>
      <Position>46</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>2411402 - Disclosure - Derivative Investments (Balance Sheet) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nationalwesternlife.com/role/DerivativeInvestmentsBalanceSheetDetails</Role>
      <ShortName>Derivative Investments (Balance Sheet) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.nationalwesternlife.com/role/DerivativeInvestmentsTables</ParentRole>
      <Position>47</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>2411403 - Disclosure - Derivative Investments (Statements of Earnings) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.nationalwesternlife.com/role/DerivativeInvestmentsStatementsOfEarningsDetails</Role>
      <ShortName>Derivative Investments (Statements of Earnings) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.nationalwesternlife.com/role/DerivativeInvestmentsTables</ParentRole>
      <Position>48</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <Logs>
    <Log type="Info">In ''Condensed Consolidated Balance Sheets'', column(s) 3, 4 are contained in other reports, so were removed by flow through suppression.</Log>
    <Log type="Info">In ''Condensed Consolidated Balance Sheets (Parenthetical)'', column(s) 4, 8, 9 are contained in other reports, so were removed by flow through suppression.</Log>
    <Log type="Info">In ''Condensed Consolidated Statements of Cash Flows'', column(s) 1, 2 are contained in other reports, so were removed by flow through suppression.</Log>
  </Logs>
  <InputFiles>
    <File>nwli-20150630.xml</File>
    <File>nwli-20150630_cal.xml</File>
    <File>nwli-20150630_def.xml</File>
    <File>nwli-20150630_lab.xml</File>
    <File>nwli-20150630_pre.xml</File>
    <File>nwli-20150630.xsd</File>
  </InputFiles>
  <SupplementalFiles/>
  <BaseTaxonomies/>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>

