DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	9 Months Ended
	Sep. 30, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation The accompanying interim condensed consolidated financial statements of the Company are unaudited. These interim condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America ("U.S. GAAP") and the applicable rules and regulations of the Securities and Exchange Commission ("SEC") for interim financial information. Accordingly, they do not include all of the information and footnotes required by U.S. GAAP for complete financial statements. The December 31, 2020 condensed consolidated balance sheet was derived from the audited financial statements as of that date, but does not include all of the information and footnotes required by U.S. GAAP for complete financial statements. The accompanying unaudited interim condensed consolidated financial statements have been prepared on the same basis as the audited consolidated financial statements and, in the opinion of management, reflect all adjustments of a normal recurring nature considered necessary to state fairly the Company's consolidated financial position, results of operations, comprehensive income (loss), and cash flows for the interim periods. The condensed consolidated financial statements include the financial statements of Square and its wholly-owned and majority-owned subsidiaries. All intercompany transactions and balances have been eliminated in consolidation. Minority interests are recorded as a noncontrolling interest, which is reported as a component of stockholders' equity on the condensed consolidated balance sheets. The interim results for the three and nine months ended September 30, 2021 are not necessarily indicative of the results that may be expected for the year ending December 31, 2021, or for any other future annual or interim period. The information included in this Quarterly Report on Form 10-Q should be read in conjunction with the Consolidated Financial Statements and related notes in the Company's Annual Report on Form 10-K for the year ended December 31, 2020.
Use of Estimates	Use of Estimates The preparation of the Company’s condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenue and expenses, as well as related disclosure of contingent assets and liabilities. Actual results could differ from the Company’s estimates. To the extent that there are material differences between these estimates and actual results, the Company’s financial condition or operating results will be materially affected. The Company bases its estimates on current and past experience, to the extent that historical experience is predictive of future performance and other assumptions that the Company believes are reasonable under the circumstances. The Company evaluates these estimates on an ongoing basis. Estimates, judgments, and assumptions in these condensed consolidated financial statements include, but are not limited to, those related to revenue recognition, accrued transaction losses, contingencies, valuation of the debt component of convertible senior notes, valuation of loans held for sale including loans under the Paycheck Protection Program ("PPP"), the allowance for loan loss reserves for loans held for investment, valuation of goodwill and acquired intangible assets, the determination of pre-acquisition contingencies associated with business combinations, accrued royalties, deferred revenue, determination of income and other taxes, operating and financing lease right-of-use assets and related liabilities, assessing the likelihood of adverse outcomes from claims and disputes, and share-based compensation.
Concentration of Credit Risk	Concentration of Credit Risk For the three and nine months ended September 30, 2021 and September 30, 2020, the Company had no customer that accounted for greater than 10% of total net revenue. The Company had two third-party payment processors that represented approximately 50% and 34% of settlements receivable as of September 30, 2021. As of December 31, 2020, there were two parties that represented approximately 59% and 27% of settlements receivable. All other third-party processors were insignificant. Financial instruments that potentially subject the Company to concentrations of credit risk consist primarily of cash and cash equivalents, restricted cash, marketable debt securities, settlements receivable, customer funds, reverse repurchase agreements, loans held for sale, and loans held for investment. The associated risk of concentration for cash and cash equivalents and restricted cash is mitigated by banking with creditworthy institutions. At certain times, amounts on deposit exceed federal deposit insurance limits. The associated risk of concentration for marketable debt securities is mitigated by holding a diversified portfolio of highly rated investments. Settlements receivable are amounts due from well-established payment processing companies and normally take one or two business days to settle which mitigates the associated risk of concentration. The associated risk with reverse repurchase agreements is mitigated by the securities held as collateral and their short-term nature. The associated risk of concentration for loans held for sale and loans held for investment are partially mitigated by credit evaluations that are performed prior to facilitating the offering of and origination of loans and ongoing performance monitoring of the Company’s loan customers. The risk associated with the PPP loans is considered low due to government guarantees on those loans.
Sales and Marketing Expenses	Sales and Marketing Expenses Advertising costs are expensed as incurred and included in sales and marketing expense in the condensed consolidated statements of operations. Total advertising costs were $123.1 million and $296.4 million for the three and nine months ended September 30, 2021, respectively, compared to $75.7 million and $145.8 million for the three and nine months ended September 30, 2020, respectively. In addition, services, incentives, and other costs to customers that are not directly related to a revenue generating transaction are recorded as sales and marketing expenses, as the Company considers these to be marketing costs to encourage the usage of Cash App. These expenses, which include, but are not limited to, Cash App peer-to-peer processing costs and related transaction losses, card issuance costs, customer referral bonuses, promotional giveaways, and certain Cash App crypto network operating costs
Recently Accounting Pronouncements	Recent Accounting Pronouncements Recently adopted accounting pronouncements In August 2020, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") No. 2020-06, Accounting for Convertible Instruments and Contracts in an Entity's Own Equity, as part of its overall simplification initiative to reduce costs and complexity of applying accounting standards while maintaining or improving the usefulness of the information provided to users of financial statements. The guidance is effective for financial statements issued for fiscal years beginning after December 15, 2021, and interim periods within those fiscal years, with early adoption permitted, but only at the beginning of the fiscal year. The Company early adopted the new guidance on January 1, 2021 using the modified retrospective approach and recorded a cumulative effect upon adoption of $103.0 million as a reduction to accumulated deficit and a reduction to other paid in capital of $502.7 million related to amounts attributable to conversion options that had previously been recorded in equity. Additionally, the Company recorded an increase to its convertible notes balance by an aggregate amount of $399.7 million as a result of the reversal of the separation of the convertible debt between debt and equity. The adoption of this standard also significantly decreased the amount of non-cash interest expense to be recognized in future periods as a result of eliminating the discount associated with the equity component. There was no impact to the Company’s statements of cash flows as the result of the adoption of ASU No. 2020-06. In October 2020, the FASB issued ASU No. 2020-10, Codification Improvements ("Codification"). The update provides incremental improvements on various topics in the Codification to provide clarification, correct errors in, and to provide simplification on a variety of topics. Among other items, the guidance includes presentation disclosures for the amount of income tax expense or benefit related to other comprehensive income. The amendments are effective for public entities in fiscal years beginning after December 15, 2020, including interim periods within those fiscal years. Early adoption is permitted. The Company adopted this guidance effective January 1, 2021 and has applied the guidance prospectively. The adoption of this guidance did not have a material impact on the Company’s financial statements and related disclosures. Recently issued accounting pronouncements not yet adopted In July 2021, the FASB issued ASU No. 2021-05 ("ASU 2021-05") "Lease (Topic 842): Lessors - Certain Leases with Variable Lease Payments" which amends the lease classification requirements for lessors with certain leases containing variable payments. A lessor should classify and account for a lease with variable lease payments that do not depend on an index or a rate as an operating lease if both of the following criteria are met: 1) the lease would have been classified as a sales-type lease or a direct financing lease; and 2) the lessor would have otherwise recognized a day-one loss. The amendments in ASU 2021-05 are effective for fiscal years beginning after December 15, 2021, with early adoption permitted. The Company is evaluating the effect of adopting this new accounting guidance, but does not expect the adoption to have a material impact on the Company’s financial statements. In May 2021, the FASB issued ASU No. 2021-04 (“ASU 2021-04”) “Earnings Per Share (Topic 260), Debt—Modifications and Extinguishments (Subtopic 470-50), Compensation— Stock Compensation (Topic 718), and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40)” which provides guidance on modifications or exchanges of a freestanding equity-classified written call option that is not within the scope of another Topic. An entity should treat a modification of the terms or conditions or an exchange of a freestanding equity-classified written call option that remains equity classified after modification or exchange as an exchange of the original instrument for a new instrument, and provides further guidance on measuring the effect of a modification or an exchange of a freestanding equity-classified written call option that remains equity classified after modification or exchange. ASU 2021-04 also provides guidance on the recognition of the effect of a modification or an exchange of a freestanding equity-classified written call option that remains equity classified after modification or exchange on the basis of the substance of the transaction, in the same manner as if cash had been paid as consideration. The amendments are effective for all entities for fiscal years beginning after December 15, 2021, including interim periods within those fiscal years. Early adoption is permitted. The Company is evaluating the effect of adopting this new accounting guidance, but does not expect adoption to have a material impact on the Company’s financial statements.
Fair Value of Financial Instruments	FAIR VALUE OF FINANCIAL INSTRUMENTSThe Company measures its cash equivalents, customer funds, short-term and long-term marketable debt securities, and marketable equity investment at fair value. The Company classifies these investments within Level 1 or Level 2 of the fair value hierarchy because the Company values these investments using quoted market prices or alternative pricing sources and models utilizing market observable inputs.