<?xml version='1.0' encoding='UTF-8'?>
<FilingSummary>
  <Version>3.8.0.1</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>76</ContextCount>
  <ElementCount>187</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>32</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>5</UnitCount>
  <MyReports>
    <Report instance="ogs-20180331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>0001000 - Document - Document And Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onegas.com/role/DocumentAndEntityInformation</Role>
      <ShortName>Document And Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="ogs-20180331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>1001000 - Statement - STATEMENTS OF INCOME</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onegas.com/role/StatementsOfIncome</Role>
      <ShortName>STATEMENTS OF INCOME</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="ogs-20180331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>1003001 - Statement - STATEMENTS OF COMPREHENSIVE INCOME STATEMENTS OF COMPREHENSIVE INCOME Parenthetical</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onegas.com/role/StatementsOfComprehensiveIncomeStatementsOfComprehensiveIncomeParenthetical</Role>
      <ShortName>STATEMENTS OF COMPREHENSIVE INCOME STATEMENTS OF COMPREHENSIVE INCOME Parenthetical</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="ogs-20180331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>1003500 - Statement - STATEMENTS OF COMPREHENSIVE INCOME STATEMENTS OF COMPREHENSIVE INCOME</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onegas.com/role/StatementsOfComprehensiveIncomeStatementsOfComprehensiveIncome</Role>
      <ShortName>STATEMENTS OF COMPREHENSIVE INCOME STATEMENTS OF COMPREHENSIVE INCOME</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="ogs-20180331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>1004000 - Statement - BALANCE SHEETS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onegas.com/role/BalanceSheets</Role>
      <ShortName>BALANCE SHEETS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="ogs-20180331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>1004001 - Statement - BALANCE SHEETS BALANCE SHEETS Parenthetical</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onegas.com/role/BalanceSheetsBalanceSheetsParenthetical</Role>
      <ShortName>BALANCE SHEETS BALANCE SHEETS Parenthetical</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="ogs-20180331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>1005000 - Statement - STATEMENTS OF CASH FLOWS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onegas.com/role/StatementsOfCashFlows</Role>
      <ShortName>STATEMENTS OF CASH FLOWS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="ogs-20180331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>1006000 - Statement - STATEMENT OF CHANGES IN EQUITY</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onegas.com/role/StatementOfChangesInEquity</Role>
      <ShortName>STATEMENT OF CHANGES IN EQUITY</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="ogs-20180331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>2101100 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES  (Notes)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.onegas.com/role/SummaryOfSignificantAccountingPoliciesNotes</Role>
      <ShortName>SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES  (Notes)</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="ogs-20180331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>2105100 - Disclosure - REVENUE (Notes)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.onegas.com/role/RevenueNotes</Role>
      <ShortName>REVENUE (Notes)</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="ogs-20180331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>2118100 - Disclosure - REGULATORY ASSETS AND LIABILITIES (Notes)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.onegas.com/role/RegulatoryAssetsAndLiabilitiesNotes</Role>
      <ShortName>REGULATORY ASSETS AND LIABILITIES (Notes)</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="ogs-20180331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>2120100 - Disclosure - CREDIT FACILITIES (Notes)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.onegas.com/role/CreditFacilitiesNotes</Role>
      <ShortName>CREDIT FACILITIES (Notes)</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="ogs-20180331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>2121100 - Disclosure - LONG-TERM DEBT (Notes)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.onegas.com/role/LongTermDebtNotes</Role>
      <ShortName>LONG-TERM DEBT (Notes)</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="ogs-20180331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>2122100 - Disclosure - EQUITY (Notes)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.onegas.com/role/EquityNotes</Role>
      <ShortName>EQUITY (Notes)</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="ogs-20180331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>2123100 - Disclosure - ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Notes)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.onegas.com/role/AccumulatedOtherComprehensiveIncomeLossNotes</Role>
      <ShortName>ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Notes)</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="ogs-20180331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>2124100 - Disclosure - EARNINGS PER SHARE (Notes)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.onegas.com/role/EarningsPerShareNotes</Role>
      <ShortName>EARNINGS PER SHARE (Notes)</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="ogs-20180331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>2125100 - Disclosure - EMPLOYEE BENEFIT PLANS (Notes)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.onegas.com/role/EmployeeBenefitPlansNotes</Role>
      <ShortName>EMPLOYEE BENEFIT PLANS (Notes)</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="ogs-20180331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>2126100 - Disclosure - INCOME TAXES (Notes)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.onegas.com/role/IncomeTaxesNotes</Role>
      <ShortName>INCOME TAXES (Notes)</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="ogs-20180331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>2127100 - Disclosure - OTHER INCOME AND OTHER EXPENSE (Notes)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.onegas.com/role/OtherIncomeAndOtherExpenseNotes</Role>
      <ShortName>OTHER INCOME AND OTHER EXPENSE (Notes)</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="ogs-20180331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>2128100 - Disclosure - COMMITMENTS AND CONTINGENCIES (Notes)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.onegas.com/role/CommitmentsAndContingenciesNotes</Role>
      <ShortName>COMMITMENTS AND CONTINGENCIES (Notes)</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="ogs-20180331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>2129100 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS (Notes)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.onegas.com/role/DerivativeFinancialInstrumentsAndFairValueMeasurementsNotes</Role>
      <ShortName>DERIVATIVE FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS (Notes)</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="ogs-20180331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>2201201 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onegas.com/role/SummaryOfSignificantAccountingPoliciesPolicies</Role>
      <ShortName>SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <Position>22</Position>
    </Report>
    <Report instance="ogs-20180331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>2229201 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS DERIVATIVE FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onegas.com/role/DerivativeFinancialInstrumentsAndFairValueMeasurementsDerivativeFinancialInstrumentsAndFairValueMeasurementsPolicies</Role>
      <ShortName>DERIVATIVE FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS DERIVATIVE FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <Position>23</Position>
    </Report>
    <Report instance="ogs-20180331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>2305301 - Disclosure - REVENUE (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onegas.com/role/RevenueTables</Role>
      <ShortName>REVENUE (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.onegas.com/role/RevenueNotes</ParentRole>
      <Position>24</Position>
    </Report>
    <Report instance="ogs-20180331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>2318301 - Disclosure - REGULATORY ASSETS AND LIABILITIES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onegas.com/role/RegulatoryAssetsAndLiabilitiesTables</Role>
      <ShortName>REGULATORY ASSETS AND LIABILITIES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.onegas.com/role/RegulatoryAssetsAndLiabilitiesNotes</ParentRole>
      <Position>25</Position>
    </Report>
    <Report instance="ogs-20180331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>2323301 - Disclosure - ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onegas.com/role/AccumulatedOtherComprehensiveIncomeLossTables</Role>
      <ShortName>ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.onegas.com/role/AccumulatedOtherComprehensiveIncomeLossNotes</ParentRole>
      <Position>26</Position>
    </Report>
    <Report instance="ogs-20180331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>2324301 - Disclosure - EARNINGS PER SHARE (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onegas.com/role/EarningsPerShareTables</Role>
      <ShortName>EARNINGS PER SHARE (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.onegas.com/role/EarningsPerShareNotes</ParentRole>
      <Position>27</Position>
    </Report>
    <Report instance="ogs-20180331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>2325301 - Disclosure - EMPLOYEE BENEFIT PLANS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onegas.com/role/EmployeeBenefitPlansTables</Role>
      <ShortName>EMPLOYEE BENEFIT PLANS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.onegas.com/role/EmployeeBenefitPlansNotes</ParentRole>
      <Position>28</Position>
    </Report>
    <Report instance="ogs-20180331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>2327301 - Disclosure - OTHER INCOME AND OTHER EXPENSE (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onegas.com/role/OtherIncomeAndOtherExpenseTables</Role>
      <ShortName>OTHER INCOME AND OTHER EXPENSE (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.onegas.com/role/OtherIncomeAndOtherExpenseNotes</ParentRole>
      <Position>29</Position>
    </Report>
    <Report instance="ogs-20180331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>2401402 - Disclosure - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onegas.com/role/SummaryOfSignificantAccountingPoliciesDetails</Role>
      <ShortName>SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.onegas.com/role/SummaryOfSignificantAccountingPoliciesPolicies</ParentRole>
      <Position>30</Position>
    </Report>
    <Report instance="ogs-20180331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>2405402 - Disclosure - REVENUE (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onegas.com/role/RevenueDetails</Role>
      <ShortName>REVENUE (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.onegas.com/role/RevenueTables</ParentRole>
      <Position>31</Position>
    </Report>
    <Report instance="ogs-20180331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>2418402 - Disclosure - REGULATORY ASSETS AND LIABILITIES (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onegas.com/role/RegulatoryAssetsAndLiabilitiesDetails</Role>
      <ShortName>REGULATORY ASSETS AND LIABILITIES (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.onegas.com/role/RegulatoryAssetsAndLiabilitiesTables</ParentRole>
      <Position>32</Position>
    </Report>
    <Report instance="ogs-20180331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>2420401 - Disclosure - CREDIT FACILITIES (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onegas.com/role/CreditFacilitiesDetails</Role>
      <ShortName>CREDIT FACILITIES (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.onegas.com/role/CreditFacilitiesNotes</ParentRole>
      <Position>33</Position>
    </Report>
    <Report instance="ogs-20180331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>2421401 - Disclosure - LONG-TERM DEBT (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onegas.com/role/LongTermDebtDetails</Role>
      <ShortName>LONG-TERM DEBT (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.onegas.com/role/LongTermDebtNotes</ParentRole>
      <Position>34</Position>
    </Report>
    <Report instance="ogs-20180331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>2422401 - Disclosure - EQUITY (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onegas.com/role/EquityDetails</Role>
      <ShortName>EQUITY (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.onegas.com/role/EquityNotes</ParentRole>
      <Position>35</Position>
    </Report>
    <Report instance="ogs-20180331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>2423402 - Disclosure - ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onegas.com/role/AccumulatedOtherComprehensiveIncomeLossDetails</Role>
      <ShortName>ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.onegas.com/role/AccumulatedOtherComprehensiveIncomeLossTables</ParentRole>
      <Position>36</Position>
    </Report>
    <Report instance="ogs-20180331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>2424402 - Disclosure - EARNINGS PER SHARE (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onegas.com/role/EarningsPerShareDetails</Role>
      <ShortName>EARNINGS PER SHARE (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.onegas.com/role/EarningsPerShareTables</ParentRole>
      <Position>37</Position>
    </Report>
    <Report instance="ogs-20180331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>2425402 - Disclosure - EMPLOYEE BENEFIT PLANS (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onegas.com/role/EmployeeBenefitPlansDetails</Role>
      <ShortName>EMPLOYEE BENEFIT PLANS (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.onegas.com/role/EmployeeBenefitPlansTables</ParentRole>
      <Position>38</Position>
    </Report>
    <Report instance="ogs-20180331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>2426401 - Disclosure - INCOME TAXES (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onegas.com/role/IncomeTaxesDetails</Role>
      <ShortName>INCOME TAXES (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.onegas.com/role/IncomeTaxesNotes</ParentRole>
      <Position>39</Position>
    </Report>
    <Report instance="ogs-20180331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>2427402 - Disclosure - OTHER INCOME AND OTHER EXPENSE (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onegas.com/role/OtherIncomeAndOtherExpenseDetails</Role>
      <ShortName>OTHER INCOME AND OTHER EXPENSE (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.onegas.com/role/OtherIncomeAndOtherExpenseTables</ParentRole>
      <Position>40</Position>
    </Report>
    <Report instance="ogs-20180331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>2428401 - Disclosure - COMMITMENTS AND CONTINGENCIES (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onegas.com/role/CommitmentsAndContingenciesDetails</Role>
      <ShortName>COMMITMENTS AND CONTINGENCIES (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.onegas.com/role/CommitmentsAndContingenciesNotes</ParentRole>
      <Position>41</Position>
    </Report>
    <Report instance="ogs-20180331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>2429402 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onegas.com/role/DerivativeFinancialInstrumentsAndFairValueMeasurementsDetails</Role>
      <ShortName>DERIVATIVE FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.onegas.com/role/DerivativeFinancialInstrumentsAndFairValueMeasurementsDerivativeFinancialInstrumentsAndFairValueMeasurementsPolicies</ParentRole>
      <Position>42</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <InputFiles>
    <File>ogs-20180331.xml</File>
    <File>ogs-20180331.xsd</File>
    <File>ogs-20180331_cal.xml</File>
    <File>ogs-20180331_def.xml</File>
    <File>ogs-20180331_lab.xml</File>
    <File>ogs-20180331_pre.xml</File>
  </InputFiles>
  <SupplementalFiles/>
  <BaseTaxonomies>
    <BaseTaxonomy>http://fasb.org/us-gaap/2016-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://xbrl.sec.gov/invest/2013-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://xbrl.sec.gov/dei/2014-01-31</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
