Summary of Significant Accounting Policies (Policies)	9 Months Ended
Summary of Significant Accounting Policies (Policies)	Sep. 30, 2017
Accounting Policies [Abstract]
Nature of Operations	Nature of Operations. Robert Half International Inc. (the “Company”) provides specialized staffing and risk consulting services through such divisions as Accountemps^®, Robert Half^® Finance & Accounting, OfficeTeam^®, Robert Half^® Technology, Robert Half^® Management Resources, Robert Half^® Legal, The Creative Group^®, and Protiviti^®. The Company, through its Accountemps, Robert Half Finance & Accounting, and Robert Half Management Resources divisions, is a specialized provider of temporary, full-time, and senior-level project professionals in the fields of accounting and finance. OfficeTeam specializes in highly skilled temporary administrative support professionals. Robert Half Technology provides project and full-time technology professionals. Robert Half Legal provides temporary, project, and full-time staffing of lawyers, paralegals and legal support personnel. The Creative Group provides interactive, design, marketing, advertising and public relations professionals. Protiviti is a global consulting firm that helps companies solve problems in finance, technology, operations, data, analytics, governance, risk and internal audit, and is a wholly-owned subsidiary of the Company. Revenues are predominantly derived from specialized staffing services. The Company operates in North America, South America, Europe, Asia and Australia. The Company is a Delaware corporation.
Basis of Presentation	Basis of Presentation. The unaudited Condensed Consolidated Financial Statements (“Financial Statements”) of the Company are prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”) and the rules of the Securities and Exchange Commission (“SEC”). The comparative year-end condensed consolidated statement of financial position data presented was derived from audited financial statements. In the opinion of management, all adjustments (consisting of only normal recurring adjustments) necessary for a fair statement of the financial position and results of operations for the periods presented have been included. These Financial Statements should be read in conjunction with the audited Consolidated Financial Statements of the Company for the year ended December 31, 2016, included in its Annual Report on Form 10-K. The results of operations for any interim period are not necessarily indicative of, nor comparable to, the results of operations for a full year.
Principles of Consolidation	Principles of Consolidation. The Financial Statements include the accounts of the Company and its subsidiaries, all of which are wholly-owned. All intercompany balances have been eliminated.
Use of Estimates	Use of Estimates. The preparation of financial statements in conformity 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 financial statements and the reported amounts of revenues and expenses during the reporting period. As of September 30, 2017, such estimates included allowances for uncollectible accounts receivable, workers’ compensation losses, and income and other taxes. Management estimates are also utilized in the Company’s goodwill impairment assessment and in the valuation of stock grants subject to market conditions. Actual results and outcomes may differ from management's estimates and assumptions.
Advertising Costs	Advertising Costs. The Company expenses all advertising costs as incurred.
New Accounting Pronouncements	Recently Adopted Accounting Pronouncements Stock Compensation. In March 2016, the Financial Accounting Standards Board ("FASB") issued authoritative guidance which changes financial reporting as it relates to Employee Share-Based Payment Accounting. Under the new guidance, several aspects of the accounting for share-based payment award transactions will be simplified, including: i) income tax consequences; ii) classification of awards as either equity or liabilities; and iii) classification on the statement of cash flows. The new guidance was effective for annual and interim periods beginning after December 15, 2016 and was adopted by the Company effective January 1, 2017. The adoption of this guidance did not have a material impact on the Company's financial statements. Recently Issued Accounting Pronouncements Not Yet Adopted Revenue from Contracts with Customers. In May 2014, the FASB issued authoritative guidance that provides companies with a single model for use in accounting for revenue arising from contracts with customers and supersedes current revenue recognition guidance, including industry-specific revenue guidance. The new guidance requires a company to recognize revenue to depict the transfer of goods or services to a customer at an amount that reflects the consideration it expects to receive in exchange for those goods or services. It also requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments and changes in judgments and assets recognized from costs incurred to obtain or fulfill a contract. The guidance permits companies to either apply the requirements retrospectively to all prior periods presented, or apply the requirements in the year of adoption, through a cumulative adjustment. The amended guidance also requires additional quantitative and qualitative disclosures. In March 2016, amended guidance was issued to clarify implementation guidance on principal versus agent consideration. In April 2016, an amendment provided clarifications on determining whether a promised license provides a customer with a right to use or a right to access an entity’s intellectual property. In May 2016, an amendment provided narrow scope improvements and practical expedients to reduce the potential diversity, cost and complexity of applying new revenue standard. These amendments, as well as the original guidance, are all effective for annual and interim periods beginning after December 15, 2017. The new standard will be effective for the Company beginning January 1, 2018 and the Company intends to implement the standard with the modified retrospective approach, which recognizes the cumulative effect of application recognized on that date. The adoption of this guidance is not expected to have a material impact on the Company's financial statements, and the Company does not anticipate significant changes to systems, processes, or controls. Lease Accounting. In February 2016, the FASB issued authoritative guidance which changes financial reporting as it relates to leasing transactions. Under the new guidance, lessees will be required to recognize a lease liability, measured on a discounted basis; and a right-of-use asset, for the lease term. The new guidance is effective for annual and interim periods beginning after December 15, 2018. Early application is permitted for all entities upon issuance. Lessees and lessors must apply a modified retrospective transition approach for leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements. While the impact of the adoption of this guidance will include the recognition of right-of-use assets and lease liabilities on the Company's statement of financial position, the Company is in the process of evaluating the impact of adoption of this guidance on its systems, processes, and controls. Classification of Certain Cash Receipts and Cash Payments in Statement of Cash Flows. In August 2016, the FASB issued authoritative guidance designed to address diversity in how certain cash receipts and cash payments are presented and classified in the statement of cash flows, including: i) contingent consideration payments made after a business combination; ii) proceeds from the settlement of insurance claims; and iii) proceeds from the settlement of corporate-owned life insurance policies. The new guidance is effective for the Company for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years. Early adoption is permitted in any interim or annual period. The Company believes the adoption of this guidance will not have a material impact on its financial statements. Simplifying the Test for Goodwill Impairment. In January 2017, the FASB issued authoritative guidance to simplify the goodwill impairment testing process. The new standard eliminates Step 2 of the goodwill impairment test. If a company determines in Step 1 of the goodwill impairment test that the carrying value of goodwill is greater than the fair value, an impairment in that amount should be recorded to the income statement, rather than proceeding to Step 2. The new guidance is effective for the Company beginning after December 31, 2019, although early adoption is permitted. The Company believes the adoption of this guidance will not have a material impact on its financial statements. Stock Compensation. In May 2017, the FASB issued authoritative guidance updating which changes in the terms or conditions of a share-based payment award require an entity to apply modification accounting. Under the amended guidance, entities are required to account for the effects of a modification if the fair value, vesting conditions or classification (as an equity instrument or a liability instrument) of the modified award change from that of the original award immediately before the modification. The new guidance is effective for the Company in interim or annual periods beginning after December 15, 2017. The Company believes the adoption of this guidance will not have a material impact on its financial statements.
Commitments and Contingencies	Legal costs associated with the resolution of claims, lawsuits and other contingencies are expensed as incurred.
Treasury Stock	The repurchased shares are held in treasury and are presented as if constructively retired. Treasury stock is accounted for using the cost method. Repurchase activity for the nine months ended September 30, 2017 and 2016, is presented in the unaudited Condensed Consolidated Statements of Stockholders’ Equity. Repurchases of shares and issuances of cash dividends are applied first to the extent of retained earnings and any remaining amounts are applied to capital surplus.