<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.21.2</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>433</ContextCount>
  <ElementCount>415</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>104</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>15</UnitCount>
  <MyReports>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>0001001 - Document - Cover Page</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/CoverPage</Role>
      <ShortName>Cover Page</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>1001002 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFOPERATIONSANDCOMPREHENSIVEINCOME</Role>
      <ShortName>CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>1002003 - Statement - CONDENSED CONSOLIDATED BALANCE SHEETS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETS</Role>
      <ShortName>CONDENSED CONSOLIDATED BALANCE SHEETS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>1003004 - Statement - CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETSParenthetical</Role>
      <ShortName>CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>1004005 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF EQUITY</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFEQUITY</Role>
      <ShortName>CONDENSED CONSOLIDATED STATEMENTS OF EQUITY</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>1005006 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFCASHFLOWS</Role>
      <ShortName>CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>2101101 - Disclosure - BASIS OF PRESENTATION</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/BASISOFPRESENTATION</Role>
      <ShortName>BASIS OF PRESENTATION</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>2104102 - Disclosure - NEW ACCOUNTING PRONOUNCEMENTS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/NEWACCOUNTINGPRONOUNCEMENTS</Role>
      <ShortName>NEW ACCOUNTING PRONOUNCEMENTS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>2106103 - Disclosure - AQUISITIONS AND DISCONTINUED OPERATIONS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/AQUISITIONSANDDISCONTINUEDOPERATIONS</Role>
      <ShortName>AQUISITIONS AND DISCONTINUED OPERATIONS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>2111104 - Disclosure - REVENUES FROM CONTRACTS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/REVENUESFROMCONTRACTS</Role>
      <ShortName>REVENUES FROM CONTRACTS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>2117105 - Disclosure - LEASES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/LEASES</Role>
      <ShortName>LEASES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>2118106 - Disclosure - INFORMATION ON REPORTABLE SEGMENTS AND OTHER OPERATING SEGMENT</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/INFORMATIONONREPORTABLESEGMENTSANDOTHEROPERATINGSEGMENT</Role>
      <ShortName>INFORMATION ON REPORTABLE SEGMENTS AND OTHER OPERATING SEGMENT</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>2121107 - Disclosure - SPECIAL CHARGES, NET</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/SPECIALCHARGESNET</Role>
      <ShortName>SPECIAL CHARGES, NET</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>2124108 - Disclosure - INVENTORIES, NET</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/INVENTORIESNET</Role>
      <ShortName>INVENTORIES, NET</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>2127109 - Disclosure - GOODWILL AND OTHER INTANGIBLE ASSETS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/GOODWILLANDOTHERINTANGIBLEASSETS</Role>
      <ShortName>GOODWILL AND OTHER INTANGIBLE ASSETS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>2132110 - Disclosure - WARRANTY</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/WARRANTY</Role>
      <ShortName>WARRANTY</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>2135111 - Disclosure - EMPLOYEE BENEFIT PLANS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/EMPLOYEEBENEFITPLANS</Role>
      <ShortName>EMPLOYEE BENEFIT PLANS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>2138112 - Disclosure - INDEBTEDNESS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/INDEBTEDNESS</Role>
      <ShortName>INDEBTEDNESS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>2142113 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/DERIVATIVEFINANCIALINSTRUMENTS</Role>
      <ShortName>DERIVATIVE FINANCIAL INSTRUMENTS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>2144114 - Disclosure - EQUITY AND LONG-TERM INCENTIVE COMPENSATION</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/EQUITYANDLONGTERMINCENTIVECOMPENSATION</Role>
      <ShortName>EQUITY AND LONG-TERM INCENTIVE COMPENSATION</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>2150115 - Disclosure - CONTINGENT LIABILITIES AND OTHER MATTERS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/CONTINGENTLIABILITIESANDOTHERMATTERS</Role>
      <ShortName>CONTINGENT LIABILITIES AND OTHER MATTERS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>2157116 - Disclosure - INCOME AND OTHER TAXES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/INCOMEANDOTHERTAXES</Role>
      <ShortName>INCOME AND OTHER TAXES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>22</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>2159117 - Disclosure - FAIR VALUE</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/FAIRVALUE</Role>
      <ShortName>FAIR VALUE</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>23</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>2163118 - Disclosure - SUBSEQUENT EVENT</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/SUBSEQUENTEVENT</Role>
      <ShortName>SUBSEQUENT EVENT</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>24</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>2202201 - Disclosure - BASIS OF PRESENTATION (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/BASISOFPRESENTATIONPolicies</Role>
      <ShortName>BASIS OF PRESENTATION (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <Position>25</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>2307301 - Disclosure - ACQUISITIONS AND DISCONTINUED OPERATIONS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/ACQUISITIONSANDDISCONTINUEDOPERATIONSTables</Role>
      <ShortName>ACQUISITIONS AND DISCONTINUED OPERATIONS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <Position>26</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>2312302 - Disclosure - REVENUES FROM CONTRACTS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/REVENUESFROMCONTRACTSTables</Role>
      <ShortName>REVENUES FROM CONTRACTS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.spx.com/role/REVENUESFROMCONTRACTS</ParentRole>
      <Position>27</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>2319303 - Disclosure - INFORMATION ON REPORTABLE SEGMENTS AND OTHER OPERATING SEGMENT (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/INFORMATIONONREPORTABLESEGMENTSANDOTHEROPERATINGSEGMENTTables</Role>
      <ShortName>INFORMATION ON REPORTABLE SEGMENTS AND OTHER OPERATING SEGMENT (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.spx.com/role/INFORMATIONONREPORTABLESEGMENTSANDOTHEROPERATINGSEGMENT</ParentRole>
      <Position>28</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>2322304 - Disclosure - SPECIAL CHARGES, NET (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/SPECIALCHARGESNETTables</Role>
      <ShortName>SPECIAL CHARGES, NET (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.spx.com/role/SPECIALCHARGESNET</ParentRole>
      <Position>29</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>2325305 - Disclosure - INVENTORIES, NET (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/INVENTORIESNETTables</Role>
      <ShortName>INVENTORIES, NET (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.spx.com/role/INVENTORIESNET</ParentRole>
      <Position>30</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>2328306 - Disclosure - GOODWILL AND OTHER INTANGIBLE ASSETS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/GOODWILLANDOTHERINTANGIBLEASSETSTables</Role>
      <ShortName>GOODWILL AND OTHER INTANGIBLE ASSETS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.spx.com/role/GOODWILLANDOTHERINTANGIBLEASSETS</ParentRole>
      <Position>31</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>2333307 - Disclosure - WARRANTY (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/WARRANTYTables</Role>
      <ShortName>WARRANTY (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.spx.com/role/WARRANTY</ParentRole>
      <Position>32</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>2336308 - Disclosure - EMPLOYEE BENEFIT PLANS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/EMPLOYEEBENEFITPLANSTables</Role>
      <ShortName>EMPLOYEE BENEFIT PLANS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.spx.com/role/EMPLOYEEBENEFITPLANS</ParentRole>
      <Position>33</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>2339309 - Disclosure - INDEBTEDNESS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/INDEBTEDNESSTables</Role>
      <ShortName>INDEBTEDNESS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.spx.com/role/INDEBTEDNESS</ParentRole>
      <Position>34</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>2345310 - Disclosure - EQUITY AND LONG-TERM INCENTIVE COMPENSATION (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/EQUITYANDLONGTERMINCENTIVECOMPENSATIONTables</Role>
      <ShortName>EQUITY AND LONG-TERM INCENTIVE COMPENSATION (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.spx.com/role/EQUITYANDLONGTERMINCENTIVECOMPENSATION</ParentRole>
      <Position>35</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>2351311 - Disclosure - CONTINGENT LIABILITIES AND OTHER MATTERS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/CONTINGENTLIABILITIESANDOTHERMATTERSTables</Role>
      <ShortName>CONTINGENT LIABILITIES AND OTHER MATTERS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.spx.com/role/CONTINGENTLIABILITIESANDOTHERMATTERS</ParentRole>
      <Position>36</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>2360312 - Disclosure - FAIR VALUE (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/FAIRVALUETables</Role>
      <ShortName>FAIR VALUE (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.spx.com/role/FAIRVALUE</ParentRole>
      <Position>37</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>2403401 - Disclosure - BASIS OF PRESENTATION (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/BASISOFPRESENTATIONDetails</Role>
      <ShortName>BASIS OF PRESENTATION (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.spx.com/role/BASISOFPRESENTATIONPolicies</ParentRole>
      <Position>38</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>2405402 - Disclosure - NEW ACCOUNTING PRONOUNCEMENTS (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/NEWACCOUNTINGPRONOUNCEMENTSDetails</Role>
      <ShortName>NEW ACCOUNTING PRONOUNCEMENTS (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.spx.com/role/NEWACCOUNTINGPRONOUNCEMENTS</ParentRole>
      <Position>39</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>2408403 - Disclosure - ACQUISITIONS AND DISCONTINUED OPERATIONS - Pre-tax Income (Loss) and After-tax Income (Loss) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/ACQUISITIONSANDDISCONTINUEDOPERATIONSPretaxIncomeLossandAftertaxIncomeLossDetails</Role>
      <ShortName>ACQUISITIONS AND DISCONTINUED OPERATIONS - Pre-tax Income (Loss) and After-tax Income (Loss) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>40</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>2409404 - Disclosure - AQUISITIONS AND DISCONTINUED OPERATIONS - Assets and Liabilities of Discontinued Operations (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/AQUISITIONSANDDISCONTINUEDOPERATIONSAssetsandLiabilitiesofDiscontinuedOperationsDetails</Role>
      <ShortName>AQUISITIONS AND DISCONTINUED OPERATIONS - Assets and Liabilities of Discontinued Operations (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>41</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>2410405 - Disclosure - ACQUISITIONS AND DISCONTINUED OPERATIONS - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/ACQUISITIONSANDDISCONTINUEDOPERATIONSNarrativeDetails</Role>
      <ShortName>ACQUISITIONS AND DISCONTINUED OPERATIONS - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>42</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>2413406 - Disclosure - REVENUES FROM CONTRACTS - Disaggregated Revenue (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/REVENUESFROMCONTRACTSDisaggregatedRevenueDetails</Role>
      <ShortName>REVENUES FROM CONTRACTS - Disaggregated Revenue (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>43</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>2414407 - Disclosure - REVENUES FROM CONTRACTS - Contract Balances (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/REVENUESFROMCONTRACTSContractBalancesDetails</Role>
      <ShortName>REVENUES FROM CONTRACTS - Contract Balances (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>44</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>2415408 - Disclosure - REVENUES FROM CONTRACTS - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/REVENUESFROMCONTRACTSNarrativeDetails</Role>
      <ShortName>REVENUES FROM CONTRACTS - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>45</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>2416409 - Disclosure - REVENUES FROM CONTRACTS - Performance Obligation Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/REVENUESFROMCONTRACTSPerformanceObligationNarrativeDetails</Role>
      <ShortName>REVENUES FROM CONTRACTS - Performance Obligation Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>46</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>2420410 - Disclosure - INFORMATION ON REPORTABLE SEGMENTS AND OTHER OPERATING SEGMENT (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/INFORMATIONONREPORTABLESEGMENTSANDOTHEROPERATINGSEGMENTDetails</Role>
      <ShortName>INFORMATION ON REPORTABLE SEGMENTS AND OTHER OPERATING SEGMENT (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.spx.com/role/INFORMATIONONREPORTABLESEGMENTSANDOTHEROPERATINGSEGMENTTables</ParentRole>
      <Position>47</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>2423411 - Disclosure - SPECIAL CHARGES, NET (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/SPECIALCHARGESNETDetails</Role>
      <ShortName>SPECIAL CHARGES, NET (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.spx.com/role/SPECIALCHARGESNETTables</ParentRole>
      <Position>48</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>2426412 - Disclosure - INVENTORIES, NET (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/INVENTORIESNETDetails</Role>
      <ShortName>INVENTORIES, NET (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.spx.com/role/INVENTORIESNETTables</ParentRole>
      <Position>49</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>2429413 - Disclosure - GOODWILL AND OTHER INTANGIBLE ASSETS - Goodwill (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/GOODWILLANDOTHERINTANGIBLEASSETSGoodwillDetails</Role>
      <ShortName>GOODWILL AND OTHER INTANGIBLE ASSETS - Goodwill (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>50</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>2430414 - Disclosure - GOODWILL AND OTHER INTANGIBLE ASSETS - Other Intangibles, Net (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/GOODWILLANDOTHERINTANGIBLEASSETSOtherIntangiblesNetDetails</Role>
      <ShortName>GOODWILL AND OTHER INTANGIBLE ASSETS - Other Intangibles, Net (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>51</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>2431415 - Disclosure - GOODWILL AND OTHER INTANGIBLE ASSETS - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/GOODWILLANDOTHERINTANGIBLEASSETSNarrativeDetails</Role>
      <ShortName>GOODWILL AND OTHER INTANGIBLE ASSETS - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>52</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>2434416 - Disclosure - WARRANTY (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/WARRANTYDetails</Role>
      <ShortName>WARRANTY (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.spx.com/role/WARRANTYTables</ParentRole>
      <Position>53</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>2437417 - Disclosure - EMPLOYEE BENEFIT PLANS (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/EMPLOYEEBENEFITPLANSDetails</Role>
      <ShortName>EMPLOYEE BENEFIT PLANS (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.spx.com/role/EMPLOYEEBENEFITPLANSTables</ParentRole>
      <Position>54</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>2440418 - Disclosure - INDEBTEDNESS - Debt Details (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/INDEBTEDNESSDebtDetailsDetails</Role>
      <ShortName>INDEBTEDNESS - Debt Details (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>55</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>2441419 - Disclosure - INDEBTEDNESS - Senior Credit Facilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/INDEBTEDNESSSeniorCreditFacilitiesDetails</Role>
      <ShortName>INDEBTEDNESS - Senior Credit Facilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>56</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>2443420 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/DERIVATIVEFINANCIALINSTRUMENTSDetails</Role>
      <ShortName>DERIVATIVE FINANCIAL INSTRUMENTS (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.spx.com/role/DERIVATIVEFINANCIALINSTRUMENTS</ParentRole>
      <Position>57</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>2446421 - Disclosure - EQUITY AND LONG-TERM INCENTIVE COMPENSATION - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/EQUITYANDLONGTERMINCENTIVECOMPENSATIONNarrativeDetails</Role>
      <ShortName>EQUITY AND LONG-TERM INCENTIVE COMPENSATION - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>58</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>2447422 - Disclosure - EQUITY AND LONG-TERM INCENTIVE COMPENSATION - Long Term Incentive Compensation (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/EQUITYANDLONGTERMINCENTIVECOMPENSATIONLongTermIncentiveCompensationDetails</Role>
      <ShortName>EQUITY AND LONG-TERM INCENTIVE COMPENSATION - Long Term Incentive Compensation (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>59</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>2448423 - Disclosure - EQUITY AND LONG-TERM INCENTIVE COMPENSATION - Accumulated Other Comprehensive Income (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/EQUITYANDLONGTERMINCENTIVECOMPENSATIONAccumulatedOtherComprehensiveIncomeDetails</Role>
      <ShortName>EQUITY AND LONG-TERM INCENTIVE COMPENSATION - Accumulated Other Comprehensive Income (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>60</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>2449424 - Disclosure - EQUITY AND LONG-TERM INCENTIVE COMPENSATION - Components of AOCI (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/EQUITYANDLONGTERMINCENTIVECOMPENSATIONComponentsofAOCIDetails</Role>
      <ShortName>EQUITY AND LONG-TERM INCENTIVE COMPENSATION - Components of AOCI (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>61</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R62.htm</HtmlFileName>
      <LongName>2452425 - Disclosure - CONTINGENT LIABILITIES AND OTHER MATTERS - General (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/CONTINGENTLIABILITIESANDOTHERMATTERSGeneralDetails</Role>
      <ShortName>CONTINGENT LIABILITIES AND OTHER MATTERS - General (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.spx.com/role/CONTINGENTLIABILITIESANDOTHERMATTERSTables</ParentRole>
      <Position>62</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R63.htm</HtmlFileName>
      <LongName>2453426 - Disclosure - CONTINGENT LIABILITIES AND OTHER MATTERS - Assets and Liabilities Related to Asbestos-related Claims (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/CONTINGENTLIABILITIESANDOTHERMATTERSAssetsandLiabilitiesRelatedtoAsbestosrelatedClaimsDetails</Role>
      <ShortName>CONTINGENT LIABILITIES AND OTHER MATTERS - Assets and Liabilities Related to Asbestos-related Claims (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>63</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R64.htm</HtmlFileName>
      <LongName>2454427 - Disclosure - CONTINGENT LIABILITIES AND OTHER MATTERS - Asbestos Product Liability Matters (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/CONTINGENTLIABILITIESANDOTHERMATTERSAsbestosProductLiabilityMattersDetails</Role>
      <ShortName>CONTINGENT LIABILITIES AND OTHER MATTERS - Asbestos Product Liability Matters (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>64</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R65.htm</HtmlFileName>
      <LongName>2455428 - Disclosure - CONTINGENT LIABILITIES AND OTHER MATTERS - Large Power Projects in South Africa (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/CONTINGENTLIABILITIESANDOTHERMATTERSLargePowerProjectsinSouthAfricaDetails</Role>
      <ShortName>CONTINGENT LIABILITIES AND OTHER MATTERS - Large Power Projects in South Africa (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>65</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R66.htm</HtmlFileName>
      <LongName>2456429 - Disclosure - CONTINGENT LIABILITIES AND OTHER MATTERS - Environmental Matters (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/CONTINGENTLIABILITIESANDOTHERMATTERSEnvironmentalMattersDetails</Role>
      <ShortName>CONTINGENT LIABILITIES AND OTHER MATTERS - Environmental Matters (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>66</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R67.htm</HtmlFileName>
      <LongName>2458430 - Disclosure - INCOME AND OTHER TAXES (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/INCOMEANDOTHERTAXESDetails</Role>
      <ShortName>INCOME AND OTHER TAXES (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.spx.com/role/INCOMEANDOTHERTAXES</ParentRole>
      <Position>67</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R68.htm</HtmlFileName>
      <LongName>2461431 - Disclosure - FAIR VALUE - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/FAIRVALUENarrativeDetails</Role>
      <ShortName>FAIR VALUE - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>68</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R69.htm</HtmlFileName>
      <LongName>2462432 - Disclosure - FAIR VALUE - Changes in Liability and Assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/FAIRVALUEChangesinLiabilityandAssetsDetails</Role>
      <ShortName>FAIR VALUE - Changes in Liability and Assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>69</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R70.htm</HtmlFileName>
      <LongName>2464433 - Disclosure - SUBSEQUENT EVENT (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.spx.com/role/SUBSEQUENTEVENTDetails</Role>
      <ShortName>SUBSEQUENT EVENT (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.spx.com/role/SUBSEQUENTEVENT</ParentRole>
      <Position>70</Position>
    </Report>
    <Report instance="spxc-20210703.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9999.htm</HtmlFileName>
      <LongName>Uncategorized Items - spxc-20210703.htm</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/role/uncategorizedFacts</Role>
      <ShortName>Uncategorized Items - spxc-20210703.htm</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>71</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="spxc-20210703.htm">spxc-20210703.htm</File>
    <File>exhibit101q22021.htm</File>
    <File>exhibit102q22021.htm</File>
    <File>exhibit311q22021.htm</File>
    <File>exhibit312q22021.htm</File>
    <File>exhibit321q22021.htm</File>
    <File>spxc-20210703.xsd</File>
    <File>spxc-20210703_cal.xml</File>
    <File>spxc-20210703_def.xml</File>
    <File>spxc-20210703_lab.xml</File>
    <File>spxc-20210703_pre.xml</File>
  </InputFiles>
  <SupplementalFiles/>
  <BaseTaxonomies>
    <BaseTaxonomy>http://fasb.org/srt/2021-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://xbrl.sec.gov/country/2021</BaseTaxonomy>
    <BaseTaxonomy>http://xbrl.sec.gov/dei/2021</BaseTaxonomy>
    <BaseTaxonomy>http://fasb.org/us-gaap/2021-01-31</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
