<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.20.2</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>169</ContextCount>
  <ElementCount>283</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>35</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>5</UnitCount>
  <MyReports>
    <Report instance="ogs-20200930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>0001001 - 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-20200930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>1001002 - 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-20200930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>1002003 - 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>3</Position>
    </Report>
    <Report instance="ogs-20200930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>1003004 - 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>4</Position>
    </Report>
    <Report instance="ogs-20200930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>1004005 - 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-20200930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>1005006 - 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-20200930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>1006007 - 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-20200930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>1007008 - 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-20200930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>2101101 - 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-20200930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>2104102 - 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-20200930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>2107103 - 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-20200930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>2110104 - 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-20200930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>2112105 - 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-20200930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>2114106 - Disclosure - LEASES (Notes)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.onegas.com/role/LEASESNotes</Role>
      <ShortName>LEASES (Notes)</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="ogs-20200930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>2116107 - Disclosure - EQUITY (Notes)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.onegas.com/role/EQUITYNotes</Role>
      <ShortName>EQUITY (Notes)</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="ogs-20200930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>2118108 - 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>16</Position>
    </Report>
    <Report instance="ogs-20200930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>2121109 - 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>17</Position>
    </Report>
    <Report instance="ogs-20200930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>2126110 - 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>18</Position>
    </Report>
    <Report instance="ogs-20200930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>2127111 - 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>19</Position>
    </Report>
    <Report instance="ogs-20200930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>2129112 - 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>20</Position>
    </Report>
    <Report instance="ogs-20200930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>2132113 - 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>21</Position>
    </Report>
    <Report instance="ogs-20200930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>2136114 - 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>22</Position>
    </Report>
    <Report instance="ogs-20200930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>2202201 - 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>23</Position>
    </Report>
    <Report instance="ogs-20200930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>2234202 - 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>24</Position>
    </Report>
    <Report instance="ogs-20200930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.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>25</Position>
    </Report>
    <Report instance="ogs-20200930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>2308302 - 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>26</Position>
    </Report>
    <Report instance="ogs-20200930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>2319303 - 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>27</Position>
    </Report>
    <Report instance="ogs-20200930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>2322304 - 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>28</Position>
    </Report>
    <Report instance="ogs-20200930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>2324305 - 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>29</Position>
    </Report>
    <Report instance="ogs-20200930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>2330306 - 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>30</Position>
    </Report>
    <Report instance="ogs-20200930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>2403401 - 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>31</Position>
    </Report>
    <Report instance="ogs-20200930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>2406402 - 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>32</Position>
    </Report>
    <Report instance="ogs-20200930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>2409403 - 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>33</Position>
    </Report>
    <Report instance="ogs-20200930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>2411404 - 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>34</Position>
    </Report>
    <Report instance="ogs-20200930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>2413405 - 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>35</Position>
    </Report>
    <Report instance="ogs-20200930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>2415406 - Disclosure - LEASES (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onegas.com/role/LEASESDetails</Role>
      <ShortName>LEASES (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.onegas.com/role/LEASESNotes</ParentRole>
      <Position>36</Position>
    </Report>
    <Report instance="ogs-20200930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>2417407 - 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>37</Position>
    </Report>
    <Report instance="ogs-20200930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>2420408 - 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>38</Position>
    </Report>
    <Report instance="ogs-20200930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>2423409 - 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>39</Position>
    </Report>
    <Report instance="ogs-20200930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>2425410 - 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>40</Position>
    </Report>
    <Report instance="ogs-20200930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>2428411 - 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>41</Position>
    </Report>
    <Report instance="ogs-20200930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>2431412 - 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>42</Position>
    </Report>
    <Report instance="ogs-20200930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>2433413 - 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>43</Position>
    </Report>
    <Report instance="ogs-20200930.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>2435414 - 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>44</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <InputFiles>
    <File doctype="10-Q" original="ogs-20200930.htm">ogs-20200930.htm</File>
    <File>ogs-20200930.xsd</File>
    <File>ogs-20200930_cal.xml</File>
    <File>ogs-20200930_def.xml</File>
    <File>ogs-20200930_lab.xml</File>
    <File>ogs-20200930_pre.xml</File>
    <File>ogsexhibit3113q10-q2020.htm</File>
    <File>ogsexhibit3123q10-q2020.htm</File>
    <File>ogsexhibit3213q10-q2020.htm</File>
    <File>ogsexhibit3223q10-q2020.htm</File>
  </InputFiles>
  <SupplementalFiles/>
  <BaseTaxonomies>
    <BaseTaxonomy>http://fasb.org/srt/2020-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://fasb.org/us-gaap/2020-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://xbrl.sec.gov/dei/2020-01-31</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
