<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.19.3</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>404</ContextCount>
  <ElementCount>520</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>93</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>12</UnitCount>
  <MyReports>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>0001000 - Document - Cover Page</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/CoverPage</Role>
      <ShortName>Cover Page</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>1001000 - Statement - CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/CondensedConsolidatedBalanceSheetsUnaudited</Role>
      <ShortName>CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>1001501 - Statement - CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/CondensedConsolidatedBalanceSheetsUnauditedParenthetical</Role>
      <ShortName>CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>1002000 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/CondensedConsolidatedStatementsOfOperationsUnaudited</Role>
      <ShortName>CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>1003000 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/CondensedConsolidatedStatementsOfComprehensiveIncomeLossUnaudited</Role>
      <ShortName>CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>1004000 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited</Role>
      <ShortName>CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>1005000 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/CondensedConsolidatedStatementsOfStockholdersEquityUnaudited</Role>
      <ShortName>CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>2101100 - Disclosure - DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/DescriptionOfBusinessAndSummaryOfSignificantAccountingPolicies</Role>
      <ShortName>DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>2102100 - Disclosure - REVENUE</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/Revenue</Role>
      <ShortName>REVENUE</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>2103100 - Disclosure - INVESTMENTS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/Investments</Role>
      <ShortName>INVESTMENTS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>2104100 - Disclosure - CUSTOMER FUNDS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/CustomerFunds</Role>
      <ShortName>CUSTOMER FUNDS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>2105100 - Disclosure - FAIR VALUE OF FINANCIAL INSTRUMENTS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/FairValueOfFinancialInstruments</Role>
      <ShortName>FAIR VALUE OF FINANCIAL INSTRUMENTS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>2106100 - Disclosure - PROPERTY AND EQUIPMENT, NET</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/PropertyAndEquipmentNet</Role>
      <ShortName>PROPERTY AND EQUIPMENT, NET</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>2107100 - Disclosure - ACQUISITIONS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/Acquisitions</Role>
      <ShortName>ACQUISITIONS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>2108100 - Disclosure - ASSETS AND LIABILITIES HELD FOR SALE</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/AssetsAndLiabilitiesHeldForSale</Role>
      <ShortName>ASSETS AND LIABILITIES HELD FOR SALE</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>2109100 - Disclosure - GOODWILL</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/Goodwill</Role>
      <ShortName>GOODWILL</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>2110100 - Disclosure - ACQUIRED INTANGIBLE ASSETS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/AcquiredIntangibleAssets</Role>
      <ShortName>ACQUIRED INTANGIBLE ASSETS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>2111100 - Disclosure - OTHER CONSOLIDATED BALANCE SHEET COMPONENTS (CURRENT)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/OtherConsolidatedBalanceSheetComponentsCurrent</Role>
      <ShortName>OTHER CONSOLIDATED BALANCE SHEET COMPONENTS (CURRENT)</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>2112100 - Disclosure - OTHER CONSOLIDATED BALANCE SHEET COMPONENTS (NON-CURRENT)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/OtherConsolidatedBalanceSheetComponentsNonCurrent</Role>
      <ShortName>OTHER CONSOLIDATED BALANCE SHEET COMPONENTS (NON-CURRENT)</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>2113100 - Disclosure - INDEBTEDNESS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/Indebtedness</Role>
      <ShortName>INDEBTEDNESS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>2114100 - Disclosure - ACCRUED TRANSACTION LOSSES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/AccruedTransactionLosses</Role>
      <ShortName>ACCRUED TRANSACTION LOSSES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>2115100 - Disclosure - INCOME TAXES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/IncomeTaxes</Role>
      <ShortName>INCOME TAXES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>22</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>2116100 - Disclosure - STOCKHOLDERS' EQUITY</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/StockholdersEquity</Role>
      <ShortName>STOCKHOLDERS' EQUITY</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>23</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>2117100 - Disclosure - NET INCOME (LOSS) PER SHARE</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/NetIncomeLossPerShare</Role>
      <ShortName>NET INCOME (LOSS) PER SHARE</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>24</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>2118100 - Disclosure - RELATED PARTY TRANSACTIONS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/RelatedPartyTransactions</Role>
      <ShortName>RELATED PARTY TRANSACTIONS</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>25</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>2119100 - Disclosure - COMMITMENTS AND CONTINGENCIES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/CommitmentsAndContingencies</Role>
      <ShortName>COMMITMENTS AND CONTINGENCIES</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>26</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>2120100 - Disclosure - SEGMENT AND GEOGRAPHICAL INFORMATION</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/SegmentAndGeographicalInformation</Role>
      <ShortName>SEGMENT AND GEOGRAPHICAL INFORMATION</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>27</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>2121100 - Disclosure - SUPPLEMENTAL CASH FLOW INFORMATION</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/SupplementalCashFlowInformation</Role>
      <ShortName>SUPPLEMENTAL CASH FLOW INFORMATION</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>28</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>2201201 - Disclosure - DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/DescriptionOfBusinessAndSummaryOfSignificantAccountingPoliciesPolicies</Role>
      <ShortName>DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <Position>29</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>2302301 - Disclosure - REVENUE (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/RevenueTables</Role>
      <ShortName>REVENUE (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://squareup.com/role/Revenue</ParentRole>
      <Position>30</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>2303301 - Disclosure - INVESTMENTS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/InvestmentsTables</Role>
      <ShortName>INVESTMENTS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://squareup.com/role/Investments</ParentRole>
      <Position>31</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>2304301 - Disclosure - CUSTOMER FUNDS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/CustomerFundsTables</Role>
      <ShortName>CUSTOMER FUNDS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://squareup.com/role/CustomerFunds</ParentRole>
      <Position>32</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>2305301 - Disclosure - FAIR VALUE OF FINANCIAL INSTRUMENTS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/FairValueOfFinancialInstrumentsTables</Role>
      <ShortName>FAIR VALUE OF FINANCIAL INSTRUMENTS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://squareup.com/role/FairValueOfFinancialInstruments</ParentRole>
      <Position>33</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>2306301 - Disclosure - PROPERTY AND EQUIPMENT, NET (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/PropertyAndEquipmentNetTables</Role>
      <ShortName>PROPERTY AND EQUIPMENT, NET (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://squareup.com/role/PropertyAndEquipmentNet</ParentRole>
      <Position>34</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>2307301 - Disclosure - ACQUISITIONS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/AcquisitionsTables</Role>
      <ShortName>ACQUISITIONS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://squareup.com/role/Acquisitions</ParentRole>
      <Position>35</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>2308301 - Disclosure - ASSETS AND LIABILITIES HELD FOR SALE (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/AssetsAndLiabilitiesHeldForSaleTables</Role>
      <ShortName>ASSETS AND LIABILITIES HELD FOR SALE (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://squareup.com/role/AssetsAndLiabilitiesHeldForSale</ParentRole>
      <Position>36</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>2309301 - Disclosure - GOODWILL (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/GoodwillTables</Role>
      <ShortName>GOODWILL (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://squareup.com/role/Goodwill</ParentRole>
      <Position>37</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>2310301 - Disclosure - ACQUIRED INTANGIBLE ASSETS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/AcquiredIntangibleAssetsTables</Role>
      <ShortName>ACQUIRED INTANGIBLE ASSETS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://squareup.com/role/AcquiredIntangibleAssets</ParentRole>
      <Position>38</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>2311301 - Disclosure - OTHER CONSOLIDATED BALANCE SHEET COMPONENTS (CURRENT) (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/OtherConsolidatedBalanceSheetComponentsCurrentTables</Role>
      <ShortName>OTHER CONSOLIDATED BALANCE SHEET COMPONENTS (CURRENT) (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://squareup.com/role/OtherConsolidatedBalanceSheetComponentsCurrent</ParentRole>
      <Position>39</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>2312301 - Disclosure - OTHER CONSOLIDATED BALANCE SHEET COMPONENTS (NON-CURRENT) (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/OtherConsolidatedBalanceSheetComponentsNonCurrentTables</Role>
      <ShortName>OTHER CONSOLIDATED BALANCE SHEET COMPONENTS (NON-CURRENT) (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://squareup.com/role/OtherConsolidatedBalanceSheetComponentsCurrent</ParentRole>
      <Position>40</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>2313301 - Disclosure - INDEBTEDNESS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/IndebtednessTables</Role>
      <ShortName>INDEBTEDNESS (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://squareup.com/role/Indebtedness</ParentRole>
      <Position>41</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>2314301 - Disclosure - ACCRUED TRANSACTION LOSSES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/AccruedTransactionLossesTables</Role>
      <ShortName>ACCRUED TRANSACTION LOSSES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://squareup.com/role/AccruedTransactionLosses</ParentRole>
      <Position>42</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>2316301 - Disclosure - STOCKHOLDERS' EQUITY (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/StockholdersEquityTables</Role>
      <ShortName>STOCKHOLDERS' EQUITY (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://squareup.com/role/StockholdersEquity</ParentRole>
      <Position>43</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>2317301 - Disclosure - NET INCOME (LOSS) PER SHARE (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/NetIncomeLossPerShareTables</Role>
      <ShortName>NET INCOME (LOSS) PER SHARE (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://squareup.com/role/NetIncomeLossPerShare</ParentRole>
      <Position>44</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>2319301 - Disclosure - COMMITMENTS AND CONTINGENCIES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/CommitmentsAndContingenciesTables</Role>
      <ShortName>COMMITMENTS AND CONTINGENCIES (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://squareup.com/role/CommitmentsAndContingencies</ParentRole>
      <Position>45</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>2320301 - Disclosure - SEGMENT AND GEOGRAPHICAL INFORMATION (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/SegmentAndGeographicalInformationTables</Role>
      <ShortName>SEGMENT AND GEOGRAPHICAL INFORMATION (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://squareup.com/role/SegmentAndGeographicalInformation</ParentRole>
      <Position>46</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>2321301 - Disclosure - SUPPLEMENTAL CASH FLOW INFORMATION (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/SupplementalCashFlowInformationTables</Role>
      <ShortName>SUPPLEMENTAL CASH FLOW INFORMATION (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://squareup.com/role/SupplementalCashFlowInformation</ParentRole>
      <Position>47</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>2401402 - Disclosure - DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/DescriptionOfBusinessAndSummaryOfSignificantAccountingPoliciesNarrativeDetails</Role>
      <ShortName>DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://squareup.com/role/DescriptionOfBusinessAndSummaryOfSignificantAccountingPoliciesPolicies</ParentRole>
      <Position>48</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>2402402 - Disclosure - REVENUE - Disaggregation of Revenue (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/RevenueDisaggregationOfRevenueDetails</Role>
      <ShortName>REVENUE - Disaggregation of Revenue (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>49</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>2402403 - Disclosure - REVENUE - Deferred Revenue (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/RevenueDeferredRevenueDetails</Role>
      <ShortName>REVENUE - Deferred Revenue (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>50</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>2403402 - Disclosure - INVESTMENTS - Short-Term and Long-Term Investments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/InvestmentsShortTermAndLongTermInvestmentsDetails</Role>
      <ShortName>INVESTMENTS - Short-Term and Long-Term Investments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>51</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>2403403 - Disclosure - INVESTMENTS - Contractual Maturities of Short-Term and Long-Term Investments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/InvestmentsContractualMaturitiesOfShortTermAndLongTermInvestmentsDetails</Role>
      <ShortName>INVESTMENTS - Contractual Maturities of Short-Term and Long-Term Investments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>52</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>2404402 - Disclosure - CUSTOMER FUNDS - Assets Underlying Customer Funds (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/CustomerFundsAssetsUnderlyingCustomerFundsDetails</Role>
      <ShortName>CUSTOMER FUNDS - Assets Underlying Customer Funds (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>53</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>2404403 - Disclosure - CUSTOMER FUNDS - Investments within Customer Funds (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/CustomerFundsInvestmentsWithinCustomerFundsDetails</Role>
      <ShortName>CUSTOMER FUNDS - Investments within Customer Funds (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>54</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>2404404 - Disclosure - CUSTOMER FUNDS - Contractual Maturities of  Investments within Customer Funds (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/CustomerFundsContractualMaturitiesOfInvestmentsWithinCustomerFundsDetails</Role>
      <ShortName>CUSTOMER FUNDS - Contractual Maturities of  Investments within Customer Funds (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>55</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>2405402 - Disclosure - FAIR VALUE OF FINANCIAL INSTRUMENTS - Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/FairValueOfFinancialInstrumentsFinancialAssetsAndLiabilitiesMeasuredAtFairValueOnRecurringBasisDetails</Role>
      <ShortName>FAIR VALUE OF FINANCIAL INSTRUMENTS - Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>56</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>2405403 - Disclosure - FAIR VALUE OF FINANCIAL INSTRUMENTS - Fair Value of Convertible Senior Notes (Details)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://squareup.com/role/FairValueOfFinancialInstrumentsFairValueOfConvertibleSeniorNotesDetails</Role>
      <ShortName>FAIR VALUE OF FINANCIAL INSTRUMENTS - Fair Value of Convertible Senior Notes (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>57</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>2405404 - Disclosure - FAIR VALUE OF FINANCIAL INSTRUMENTS - Fair Value of Loans Held for Sale (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/FairValueOfFinancialInstrumentsFairValueOfLoansHeldForSaleDetails</Role>
      <ShortName>FAIR VALUE OF FINANCIAL INSTRUMENTS - Fair Value of Loans Held for Sale (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>58</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>2406402 - Disclosure - PROPERTY AND EQUIPMENT, NET (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/PropertyAndEquipmentNetDetails</Role>
      <ShortName>PROPERTY AND EQUIPMENT, NET (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://squareup.com/role/PropertyAndEquipmentNetTables</ParentRole>
      <Position>59</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>2407402 - Disclosure - ACQUISITIONS - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/AcquisitionsNarrativeDetails</Role>
      <ShortName>ACQUISITIONS - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>60</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>2407403 - Disclosure - ACQUISITIONS - Schedule of Assets Acquired and Liabilities Assumed (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/AcquisitionsScheduleOfAssetsAcquiredAndLiabilitiesAssumedDetails</Role>
      <ShortName>ACQUISITIONS - Schedule of Assets Acquired and Liabilities Assumed (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>61</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R62.htm</HtmlFileName>
      <LongName>2408402 - Disclosure - ASSETS AND LIABILITIES HELD FOR SALE - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/AssetsAndLiabilitiesHeldForSaleNarrativeDetails</Role>
      <ShortName>ASSETS AND LIABILITIES HELD FOR SALE - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>62</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R63.htm</HtmlFileName>
      <LongName>2408403 - Disclosure - ASSETS AND LIABILITIES HELD FOR SALE - Carrying Values of Assets and Liabilities Held for Sale (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/AssetsAndLiabilitiesHeldForSaleCarryingValuesOfAssetsAndLiabilitiesHeldForSaleDetails</Role>
      <ShortName>ASSETS AND LIABILITIES HELD FOR SALE - Carrying Values of Assets and Liabilities Held for Sale (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>63</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R64.htm</HtmlFileName>
      <LongName>2409402 - Disclosure - GOODWILL (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/GoodwillDetails</Role>
      <ShortName>GOODWILL (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://squareup.com/role/GoodwillTables</ParentRole>
      <Position>64</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R65.htm</HtmlFileName>
      <LongName>2410402 - Disclosure - ACQUIRED INTANGIBLE ASSETS - Schedule of Acquired Intangible Assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/AcquiredIntangibleAssetsScheduleOfAcquiredIntangibleAssetsDetails</Role>
      <ShortName>ACQUIRED INTANGIBLE ASSETS - Schedule of Acquired Intangible Assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>65</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R66.htm</HtmlFileName>
      <LongName>2410403 - Disclosure - ACQUIRED INTANGIBLE ASSETS  - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/AcquiredIntangibleAssetsNarrativeDetails</Role>
      <ShortName>ACQUIRED INTANGIBLE ASSETS  - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>66</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R67.htm</HtmlFileName>
      <LongName>2410404 - Disclosure - ACQUIRED INTANGIBLE ASSETS - Change in Carrying Value of Intangible Assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/AcquiredIntangibleAssetsChangeInCarryingValueOfIntangibleAssetsDetails</Role>
      <ShortName>ACQUIRED INTANGIBLE ASSETS - Change in Carrying Value of Intangible Assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>67</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R68.htm</HtmlFileName>
      <LongName>2410405 - Disclosure - ACQUIRED INTANGIBLE ASSETS  - Future Amortization Expense of Intangible Assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/AcquiredIntangibleAssetsFutureAmortizationExpenseOfIntangibleAssetsDetails</Role>
      <ShortName>ACQUIRED INTANGIBLE ASSETS  - Future Amortization Expense of Intangible Assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>68</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R69.htm</HtmlFileName>
      <LongName>2411402 - Disclosure - OTHER CONSOLIDATED BALANCE SHEET COMPONENTS (CURRENT) - Other Current Assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/OtherConsolidatedBalanceSheetComponentsCurrentOtherCurrentAssetsDetails</Role>
      <ShortName>OTHER CONSOLIDATED BALANCE SHEET COMPONENTS (CURRENT) - Other Current Assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://squareup.com/role/OtherConsolidatedBalanceSheetComponentsCurrentTables</ParentRole>
      <Position>69</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R70.htm</HtmlFileName>
      <LongName>2411403 - Disclosure - OTHER CONSOLIDATED BALANCE SHEET COMPONENTS (CURRENT) - Accrued Expenses (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/OtherConsolidatedBalanceSheetComponentsCurrentAccruedExpensesDetails</Role>
      <ShortName>OTHER CONSOLIDATED BALANCE SHEET COMPONENTS (CURRENT) - Accrued Expenses (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://squareup.com/role/OtherConsolidatedBalanceSheetComponentsCurrentTables</ParentRole>
      <Position>70</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R71.htm</HtmlFileName>
      <LongName>2411404 - Disclosure - OTHER CONSOLIDATED BALANCE SHEET COMPONENTS (CURRENT) - Other Current Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/OtherConsolidatedBalanceSheetComponentsCurrentOtherCurrentLiabilitiesDetails</Role>
      <ShortName>OTHER CONSOLIDATED BALANCE SHEET COMPONENTS (CURRENT) - Other Current Liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://squareup.com/role/OtherConsolidatedBalanceSheetComponentsCurrentTables</ParentRole>
      <Position>71</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R72.htm</HtmlFileName>
      <LongName>2412402 - Disclosure - OTHER CONSOLIDATED BALANCE SHEET COMPONENTS (NON-CURRENT) - Other Non-Current Assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/OtherConsolidatedBalanceSheetComponentsNonCurrentOtherNonCurrentAssetsDetails</Role>
      <ShortName>OTHER CONSOLIDATED BALANCE SHEET COMPONENTS (NON-CURRENT) - Other Non-Current Assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://squareup.com/role/OtherConsolidatedBalanceSheetComponentsCurrentTables</ParentRole>
      <Position>72</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R73.htm</HtmlFileName>
      <LongName>2412403 - Disclosure - OTHER CONSOLIDATED BALANCE SHEET COMPONENTS (NON-CURRENT) - Other Non-Current Liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/OtherConsolidatedBalanceSheetComponentsNonCurrentOtherNonCurrentLiabilitiesDetails</Role>
      <ShortName>OTHER CONSOLIDATED BALANCE SHEET COMPONENTS (NON-CURRENT) - Other Non-Current Liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://squareup.com/role/OtherConsolidatedBalanceSheetComponentsCurrentTables</ParentRole>
      <Position>73</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R74.htm</HtmlFileName>
      <LongName>2413402 - Disclosure - INDEBTEDNESS - Revolving Credit Facility Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/IndebtednessRevolvingCreditFacilityNarrativeDetails</Role>
      <ShortName>INDEBTEDNESS - Revolving Credit Facility Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>74</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R75.htm</HtmlFileName>
      <LongName>2413403 - Disclosure - INDEBTEDNESS - Convertible Senior Notes Narrative (Details)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://squareup.com/role/IndebtednessConvertibleSeniorNotesNarrativeDetails</Role>
      <ShortName>INDEBTEDNESS - Convertible Senior Notes Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>75</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R76.htm</HtmlFileName>
      <LongName>2413404 - Disclosure - INDEBTEDNESS - Net Carrying Amount of Convertible Notes (Details)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://squareup.com/role/IndebtednessNetCarryingAmountOfConvertibleNotesDetails</Role>
      <ShortName>INDEBTEDNESS - Net Carrying Amount of Convertible Notes (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>76</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R77.htm</HtmlFileName>
      <LongName>2413405 - Disclosure - INDEBTEDNESS - Carrying Amount of Equity Component of Convertible Notes (Details)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://squareup.com/role/IndebtednessCarryingAmountOfEquityComponentOfConvertibleNotesDetails</Role>
      <ShortName>INDEBTEDNESS - Carrying Amount of Equity Component of Convertible Notes (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>77</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R78.htm</HtmlFileName>
      <LongName>2413406 - Disclosure - INDEBTEDNESS - Interest Expense on Convertible Notes (Details)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://squareup.com/role/IndebtednessInterestExpenseOnConvertibleNotesDetails</Role>
      <ShortName>INDEBTEDNESS - Interest Expense on Convertible Notes (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>78</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R79.htm</HtmlFileName>
      <LongName>2413407 - Disclosure - INDEBTEDNESS - Convertible Note Hedge and Warrant Transactions (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/IndebtednessConvertibleNoteHedgeAndWarrantTransactionsDetails</Role>
      <ShortName>INDEBTEDNESS - Convertible Note Hedge and Warrant Transactions (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>79</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R80.htm</HtmlFileName>
      <LongName>2414402 - Disclosure - ACCRUED TRANSACTION LOSSES (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/AccruedTransactionLossesDetails</Role>
      <ShortName>ACCRUED TRANSACTION LOSSES (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://squareup.com/role/AccruedTransactionLossesTables</ParentRole>
      <Position>80</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R81.htm</HtmlFileName>
      <LongName>2415401 - Disclosure - INCOME TAXES (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/IncomeTaxesDetails</Role>
      <ShortName>INCOME TAXES (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://squareup.com/role/IncomeTaxes</ParentRole>
      <Position>81</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R82.htm</HtmlFileName>
      <LongName>2416402 - Disclosure - STOCKHOLDERS' EQUITY - Common Stock and Warrants Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/StockholdersEquityCommonStockAndWarrantsNarrativeDetails</Role>
      <ShortName>STOCKHOLDERS' EQUITY - Common Stock and Warrants Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>82</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R83.htm</HtmlFileName>
      <LongName>2416403 - Disclosure - STOCKHOLDERS' EQUITY - Stock Plans and Share Based Compensation Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/StockholdersEquityStockPlansAndShareBasedCompensationNarrativeDetails</Role>
      <ShortName>STOCKHOLDERS' EQUITY - Stock Plans and Share Based Compensation Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>83</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R84.htm</HtmlFileName>
      <LongName>2416404 - Disclosure - STOCKHOLDERS' EQUITY - Stock Option Activity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/StockholdersEquityStockOptionActivityDetails</Role>
      <ShortName>STOCKHOLDERS' EQUITY - Stock Option Activity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>84</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R85.htm</HtmlFileName>
      <LongName>2416405 - Disclosure - STOCKHOLDERS' EQUITY - Restricted Stock Awards and Restricted Stock Units Activity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/StockholdersEquityRestrictedStockAwardsAndRestrictedStockUnitsActivityDetails</Role>
      <ShortName>STOCKHOLDERS' EQUITY - Restricted Stock Awards and Restricted Stock Units Activity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>85</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R86.htm</HtmlFileName>
      <LongName>2416406 - Disclosure - STOCKHOLDERS' EQUITY - Stock Option Fair Value Assumptions (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/StockholdersEquityStockOptionFairValueAssumptionsDetails</Role>
      <ShortName>STOCKHOLDERS' EQUITY - Stock Option Fair Value Assumptions (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>86</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R87.htm</HtmlFileName>
      <LongName>2416407 - Disclosure - STOCKHOLDERS' EQUITY - Effects of Share-Based Compensation on Statements of Operations (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/StockholdersEquityEffectsOfShareBasedCompensationOnStatementsOfOperationsDetails</Role>
      <ShortName>STOCKHOLDERS' EQUITY - Effects of Share-Based Compensation on Statements of Operations (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>87</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R88.htm</HtmlFileName>
      <LongName>2417402 - Disclosure - NET INCOME (LOSS) PER SHARE - Calculation of Basic and Diluted Net Loss Per Share (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/NetIncomeLossPerShareCalculationOfBasicAndDilutedNetLossPerShareDetails</Role>
      <ShortName>NET INCOME (LOSS) PER SHARE - Calculation of Basic and Diluted Net Loss Per Share (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://squareup.com/role/NetIncomeLossPerShareTables</ParentRole>
      <Position>88</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R89.htm</HtmlFileName>
      <LongName>2417403 - Disclosure - NET INCOME (LOSS) PER SHARE - Antidilutive Securities Excluded from Computation of Diluted Net Income (Loss) Per Share (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/NetIncomeLossPerShareAntidilutiveSecuritiesExcludedFromComputationOfDilutedNetIncomeLossPerShareDetails</Role>
      <ShortName>NET INCOME (LOSS) PER SHARE - Antidilutive Securities Excluded from Computation of Diluted Net Income (Loss) Per Share (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://squareup.com/role/NetIncomeLossPerShareTables</ParentRole>
      <Position>89</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R90.htm</HtmlFileName>
      <LongName>2418401 - Disclosure - RELATED PARTY TRANSACTIONS (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/RelatedPartyTransactionsDetails</Role>
      <ShortName>RELATED PARTY TRANSACTIONS (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://squareup.com/role/RelatedPartyTransactions</ParentRole>
      <Position>90</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R91.htm</HtmlFileName>
      <LongName>2419402 - Disclosure - COMMITMENTS AND CONTINGENCIES - Operating and Finance Leases Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/CommitmentsAndContingenciesOperatingAndFinanceLeasesNarrativeDetails</Role>
      <ShortName>COMMITMENTS AND CONTINGENCIES - Operating and Finance Leases Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>91</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R92.htm</HtmlFileName>
      <LongName>2419403 - Disclosure - COMMITMENTS AND CONTINGENCIES - Schedule of Lease Expense Components (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/CommitmentsAndContingenciesScheduleOfLeaseExpenseComponentsDetails</Role>
      <ShortName>COMMITMENTS AND CONTINGENCIES - Schedule of Lease Expense Components (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>92</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R93.htm</HtmlFileName>
      <LongName>2419404 - Disclosure - COMMITMENTS AND CONTINGENCIES - Other Information Related to Leases (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/CommitmentsAndContingenciesOtherInformationRelatedToLeasesDetails</Role>
      <ShortName>COMMITMENTS AND CONTINGENCIES - Other Information Related to Leases (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>93</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R94.htm</HtmlFileName>
      <LongName>2419405 - Disclosure - COMMITMENTS AND CONTINGENCIES - Cash Flows Related to Leases (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/CommitmentsAndContingenciesCashFlowsRelatedToLeasesDetails</Role>
      <ShortName>COMMITMENTS AND CONTINGENCIES - Cash Flows Related to Leases (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>94</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R95.htm</HtmlFileName>
      <LongName>2419406 - Disclosure - COMMITMENTS AND CONTINGENCIES - Schedule of Future Minimum Lease Payments Under Non-Cancelable Operating Leases and Finance Leases (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/CommitmentsAndContingenciesScheduleOfFutureMinimumLeasePaymentsUnderNonCancelableOperatingLeasesAndFinanceLeasesDetails</Role>
      <ShortName>COMMITMENTS AND CONTINGENCIES - Schedule of Future Minimum Lease Payments Under Non-Cancelable Operating Leases and Finance Leases (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>95</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R96.htm</HtmlFileName>
      <LongName>2419407 - Disclosure - COMMITMENTS AND CONTINGENCIES - Litigation (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/CommitmentsAndContingenciesLitigationDetails</Role>
      <ShortName>COMMITMENTS AND CONTINGENCIES - Litigation (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>96</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R97.htm</HtmlFileName>
      <LongName>2420402 - Disclosure - SEGMENT AND GEOGRAPHICAL INFORMATION - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/SegmentAndGeographicalInformationNarrativeDetails</Role>
      <ShortName>SEGMENT AND GEOGRAPHICAL INFORMATION - Narrative (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>97</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R98.htm</HtmlFileName>
      <LongName>2420403 - Disclosure - SEGMENT AND GEOGRAPHICAL INFORMATION  - Revenue by Geographic Area (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/SegmentAndGeographicalInformationRevenueByGeographicAreaDetails</Role>
      <ShortName>SEGMENT AND GEOGRAPHICAL INFORMATION  - Revenue by Geographic Area (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>98</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R99.htm</HtmlFileName>
      <LongName>2420404 - Disclosure - SEGMENT AND GEOGRAPHICAL INFORMATION - Long-lived Assets by Geographic Area (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/SegmentAndGeographicalInformationLongLivedAssetsByGeographicAreaDetails</Role>
      <ShortName>SEGMENT AND GEOGRAPHICAL INFORMATION - Long-lived Assets by Geographic Area (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>99</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R100.htm</HtmlFileName>
      <LongName>2421402 - Disclosure - SUPPLEMENTAL CASH FLOW INFORMATION (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://squareup.com/role/SupplementalCashFlowInformationDetails</Role>
      <ShortName>SUPPLEMENTAL CASH FLOW INFORMATION (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://squareup.com/role/SupplementalCashFlowInformationTables</ParentRole>
      <Position>100</Position>
    </Report>
    <Report instance="q3fy19squareinc10-q.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9999.htm</HtmlFileName>
      <LongName>Uncategorized Items - q3fy19squareinc10-q.htm</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/role/uncategorizedFacts</Role>
      <ShortName>Uncategorized Items - q3fy19squareinc10-q.htm</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>101</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="q3fy19squareinc10-q.htm">q3fy19squareinc10-q.htm</File>
    <File>exhibit311q3191.htm</File>
    <File>exhibit312q319.htm</File>
    <File>exhibit321q3191.htm</File>
    <File>sq-20190930.xsd</File>
    <File>sq-20190930_cal.xml</File>
    <File>sq-20190930_def.xml</File>
    <File>sq-20190930_lab.xml</File>
    <File>sq-20190930_pre.xml</File>
  </InputFiles>
  <SupplementalFiles/>
  <BaseTaxonomies>
    <BaseTaxonomy>http://fasb.org/us-gaap/2019-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://fasb.org/srt/2019-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://xbrl.sec.gov/dei/2019-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://xbrl.sec.gov/country/2017-01-31</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
