Summary of Business and Significant Accounting Policies (Policies)	6 Months Ended
	Oct. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation and Principles of Consolidation The Company prepares its unaudited condensed consolidated financial statements in accordance with generally accepted accounting principles in the United States (“U.S. GAAP”) and applicable rules and regulations of the U.S. Securities and Exchange Commission (the “SEC”) regarding interim financial reporting. Accordingly, they do not include all disclosures normally required in annual consolidated financial statements prepared in accordance with U.S. GAAP. Therefore, these unaudited condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes included in the Company’s Annual Report on Form 10-K for the fiscal year ended April 30, 2021, which was filed with the SEC on June 25, 2021. In management’s opinion, these unaudited condensed consolidated financial statements have been prepared on the same basis as the annual financial statements and reflect all adjustments, which include only normal recurring adjustments necessary for the fair statement of the Company’s financial position as of October 31, 2021, and the results of operations for the three and six months ended October 31, 2021. The results of operations for the three and six months ended October 31, 2021, are not necessarily indicative of the results to be expected for the full year or any other future interim or annual period.
Principles of Consolidation	The condensed consolidated financial statements include the accounts of C3.ai, Inc. and its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation.
Use of Estimates	Use of Estimates The preparation of the accompanying unaudited condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions about future events. These estimates and the underlying assumptions affect the amounts of assets and liabilities reported, disclosures about contingent assets and liabilities, and reported amounts of revenue and expenses. Actual results and outcomes could differ significantly from the Company’s estimates, judgments, and assumptions. Significant estimates include determining standalone selling price for performance obligations in contracts with customers and estimating variable consideration, the estimated expected benefit period for deferred contract acquisition costs, the useful lives of long-lived assets and other assumptions used to measure stock-based compensation, and the valuation of deferred income tax assets and uncertain tax positions. These estimates and assumptions are based on management’s best estimates and judgment. Management evaluates its estimates and assumptions on an ongoing basis using historical experience and other factors, including the current economic environment, which management believes to be reasonable under the circumstances. The Company adjusts such estimates and assumptions when facts and circumstances dictate. Changes in those estimates resulting from continuing changes in the economic environment will be reflected in the financial statements in future periods. As future events and their effects cannot be determined with precision, actual results could materially differ from those estimates and assumptions.
Fiscal Year	Fiscal YearThe Company’s fiscal year ends on April 30.
Recent Accounting Pronouncements and Recently Adopted Accounting Standards	Recent Accounting Pronouncements The Company currently qualifies as an “emerging growth company” under the Jumpstart Our Business Startups Act of 2012 (the “JOBS Act”). Accordingly, the Company is provided the option to adopt new or revised accounting guidance either (1) within the same periods as those otherwise applicable to public business entities or (2) within the same time periods as private companies, including early adoption when permissible. The Company has elected to adopt new or revised accounting guidance within the same time period as private companies. Based on the market value of our Class A common stock held by non-affiliates as of the last business day of the Company’s fiscal second quarter ended October 31, 2021, the Company will cease to be an emerging growth company as of April 30, 2022. Recently Adopted Accounting Standards In August 2018, the FASB issued ASU 2018-15, Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement that is a Service Contract, which requires a customer in a cloud computing arrangement that is a service contract to follow the internal-use software guidance in ASC 350-40 to determine which implementation costs to defer and recognize as an asset. The guidance is effective for the fiscal year beginning May 1, 2021. Early adoption is permitted. The Company adopted this guidance effective May 1, 2021 on a prospective basis, and the adoption did not have a material impact on its condensed consolidated financial statements and related disclosures. In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740)—Simplifying the Accounting for Income Taxes. The amendments in this update simplify various aspects of the accounting for income tax by eliminating certain exceptions to the general approach under existing accounting guidance provided by ASC 740, Income Taxes, and clarifies certain aspects of the existing guidance to promote more consistent application. The amendments in this new standard include, the elimination of exceptions related to the approach for intraperiod tax allocation, the methodology for calculating income taxes in an interim period and the recognition of deferred tax liabilities for outside basis differences. The new standard also simplifies aspects of the accounting for franchise taxes and enacted changes in tax laws or rates and clarifies the accounting for transactions that result in a step-up in the tax basis of goodwill and that single-member limited liability companies and similar disregarded entities that are not subject to income tax are not required to recognize an allocation of consolidated income tax expense in their separate financial statements, but could elect to do so. The guidance is effective for the Company beginning May 1, 2022. Early adoption is permitted. The Company adopted this guidance effective May 1, 2021, and the adoption did not have a material impact on its condensed consolidated financial statements and related disclosures.