Description of Business and Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2025
Accounting Policies [Abstract]
Description of Business and Summary of Significant Accounting Policies	Description of Business and Summary of Significant Accounting Policies Five9, Inc. and its wholly-owned subsidiaries (the “Company”) is a provider of cloud software for contact centers. The Company was incorporated in Delaware in 2001 and is headquartered in San Ramon, California. The Company has offices in Europe, Asia and Australia, which primarily provide research, development, sales, marketing, and customer support services. Basis of Presentation The accompanying condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States (“GAAP”) and applicable rules and regulations of the Securities and Exchange Commission (“SEC”) regarding interim financial reporting. Certain information and note disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. Therefore, these condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2024. In the opinion of management, the condensed consolidated financial statements reflect all adjustments, which are normal and recurring in nature, necessary for fair financial statement presentation. All intercompany transactions and balances have been eliminated in consolidation. Use of Estimates The preparation of condensed consolidated financial statements in accordance with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements and the reported amounts of revenue and expenses during the reporting period. The significant estimates made by management affect revenue and related reserves, as well as the fair value of assets acquired and liabilities assumed through business combinations and the fair value of performance-based restricted stock units ("PRSUs"). Management periodically evaluates such estimates and they are adjusted prospectively based upon such periodic evaluation. Actual results could differ from those estimates. Significant Accounting Policies There have been no material changes from the significant accounting policies previously disclosed in Part II, Item 8, of the Company's Annual Report on Form 10-K for the fiscal year ended December 31, 2024 as filed with the SEC on February 21, 2025. Recent Accounting Pronouncements Not Yet Effective In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures. This ASU requires disclosure of specific categories in the effective tax rate reconciliation and additional information on income taxes paid. This ASU is effective for the Company’s fiscal years beginning after December 15, 2024. Early adoption is permitted and may be adopted on a prospective or retrospective basis. The Company is currently evaluating the impact of this ASU on its consolidated financial statement disclosures. In November 2024, the FASB issued ASU 2024-03, Income Statement - Reporting Comprehensive Income - Expense Disaggregation Disclosures (Subtopic 220-40), and in January 2025, the FASB issued ASU 2025-01, Income Statement - Reporting Comprehensive Income - Expense Disaggregation Disclosures (Subtopic 220-40): Clarifying the Effective Date, which clarified the effective date of ASU 2024-03. This ASU is intended to improve the decision-usefulness of expense information on public companies’ income statements through disaggregation of relevant expense captions in the notes to the financial statements. The guidance, as clarified by ASU 2025-01, is effective for annual reporting periods beginning after December 15, 2026, and interim periods within annual reporting periods beginning after December 15, 2027, with early adoption permitted. The Company is currently assessing the impact of this ASU on its consolidated financial statements and related disclosures. In November 2024, the FASB issued ASU 2024-04, Debt with Conversion and Other Options (Subtopic 470-20), which clarifies the requirements for determining whether certain settlements of convertible debt instruments should be accounted for as an induced conversion. The ASU is effective for annual and interim reporting periods beginning after December 15, 2025. Early adoption is permitted for entities that have implemented ASU 2020-06, with the option to apply the guidance prospectively or retrospectively. The Company is currently assessing the impact of this ASU on its consolidated financial statements.