Basis of Presentation	9 Months Ended
Basis of Presentation	Sep. 30, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation Basis of Presentation — The accompanying unaudited consolidated financial statements include the accounts of Bentley Systems, Incorporated (“Bentley” or the “Company”) and its wholly-owned subsidiaries, and have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and in accordance with the rules and regulations of the United States Securities and Exchange Commission (“SEC”) regarding interim financial reporting. Accordingly, they do not include all the information and notes required by U.S. GAAP for annual financial statements. These unaudited consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto included in Part II, Item 8 of the Company’s 2021 Annual Report on Form 10‑K on file with the SEC. In management’s opinion, the accompanying unaudited consolidated financial statements contain all adjustments (consisting of normal, recurring and non-recurring adjustments) that were considered necessary for the fair statement of the Company’s financial position, results of operations, and cash flows at the dates and for the periods indicated. The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect reported amounts in the financial statements and accompanying notes. Actual results could differ materially from those estimates. The December 31, 2021 consolidated balance sheet included herein is derived from the Company’s audited consolidated financial statements. Certain reclassifications of prior period amounts have been made to conform to the current period presentation. Business Combinations — On January 31, 2022, the Company completed the acquisition of Power Line Systems, a leader in software for the design of overhead electric power transmission lines and their structures, for $695,968 in cash, net of cash acquired. On June 17, 2021, the Company completed the acquisition of Seequent Holdings Limited (“Seequent”), a leader in software for geological and geophysical modeling, geotechnical stability, and cloud services for geodata management and collaboration, for $883,336 in cash, net of cash acquired, plus 3,141,342 shares of the Company’s Class B Common Stock (see Note 4). Deferred Compensation — Under the Company’s unfunded amended and restated Bentley Systems, Incorporated Nonqualified Deferred Compensation Plan (the “DCP”), certain officers and key employees may defer all or any part of their incentive compensation, and the Company may make discretionary awards on behalf of such participants. Elective participant deferrals and discretionary Company awards are received in the form of phantom shares of the Company’s Class B Common Stock, which are valued for tax and accounting purposes in the same manner as actual shares of Class B Common Stock, and are recorded as stock‑based compensation expense in the consolidated statements of operations (see Note 15). In August 2021, the Company’s Board of Directors approved an amendment to the DCP, which offered to certain active executives in the DCP a one‑time, short‑term election to reallocate a limited portion of their DCP holdings from phantom shares of the Company’s Class B Common Stock into other phantom investment funds. The offer to reallocate was subject to a proration mechanism which adjusted the aggregate elections to a maximum of 1,500,000 phantom shares of the Company’s Class B Common Stock. This resulted in a reduction of 1,500,000 shares in both the basic and diluted count of Company shares. While DCP participants’ investments in phantom shares remain equity classified, as they will be settled in shares of Class B Common Stock upon eventual distribution, the amendment and elections resulted in a change to liability classification for the reallocated phantom investments, as they will be settled in cash upon eventual distribution. As a result, during the three and nine months ended September 30, 2021, the Company reclassified cumulative compensation cost of $4,739 from Additional paid-in capital to Accruals and other current liabilities or Deferred compensation plan liabilities in the consolidated balance sheet and recognized a compensation charge of $90,721 to Deferred compensation plan expenses in the consolidated statements of operations to record the reallocated deferred compensation plan liabilities at their fair value of $95,460. Subsequent to the one‑time reallocation, these diversified deferred compensation plan liabilities are marked to market at the end of each reporting period, with changes in the liabilities recorded as an expense (income) to Deferred compensation plan in the consolidated statements of operations (see Note 12).