Significant Accounting Policies (Policies)	12 Months Ended
Significant Accounting Policies (Policies)	Dec. 31, 2016
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation - The consolidated financial statements of the Company and the accompanying notes are prepared in accordance with U.S. generally accepted accounting principles (GAAP).
Principles of Consolidation	Principles of Consolidation - The consolidated financial statements include the accounts of CDI Corp. and its wholly-owned subsidiaries. All significant intercompany balances and transactions 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 disclosed in the financial statements and accompanying notes. Estimates, by their nature, are based on judgment and available information. Actual results could differ materially from those estimates. Significant estimates inherent in the preparation of the accompanying consolidated financial statements include the assumptions used in the determination of the allowance for doubtful accounts receivable, impairment assessment of goodwill, determination of the recoverability of long-lived assets, assessment of legal contingencies and calculation of income taxes.
Revenue Recognition	Revenue Recognition - Revenue is presented net of any revenue-based taxes, such as sales, use, excise and value added taxes. The Company derives its revenue from several sources. Each of the Company’s four segments provide staffing services. The Company’s Engineering Solutions and Specialty Talent and Technology Solutions segments also provide project and managed outsourcing services, which include cost-plus and fixed-price contracts, and on-site engineering services. The Company’s Management Recruiters International (MRI) segment also generates franchising revenue through royalties and, to a lesser extent, initial franchise fees. Staffing Services - The Company recognizes revenue from staffing services based on the gross amount billed. The Company typically bills its customers once services are performed and associated costs have been incurred. In these circumstances, the Company assumes the risk of acceptability of its employees to its customers. The Company will also at times use unaffiliated companies (supplier associates) and their employees to fulfill a customer’s staffing requirements either in whole or in part. Under these arrangements, these firms serve as subcontractors. Customers typically require a single consolidated bill that reflects services performed by both the Company’s employees and the employees of any applicable supplier associates. When utilizing supplier associates, the Company records the difference between its gross billings and the amount paid to the supplier associate as revenue, which is generally referred to as an administrative fee. Administrative and clerical costs related to time accumulation, invoicing and other activities are recorded and included in operating and administrative expenses as incurred. Project and Managed Outsourcing Services - The Company recognizes revenue from project and managed outsourcing services as the services are performed. Revenue for these services is generally based on mark-ups of the Company's employees' hourly rates of pay or on a cost plus fixed fee basis. Information technology (IT) managed outsourcing service contracts generally include the performance of certain computer or network operations or service-desk support on behalf of customers. These IT managed outsourcing service contracts typically contain an invoicing schedule covering the contractual period. Accordingly, the Company recognizes revenue on a pro-rata basis using elapsed time as the measure of performance under these IT managed outsourcing service contracts. The Company derives less than 3% of its revenue from fixed-price contracts. Fixed-price engineering contracts typically include development of conceptual and detailed designs in support of a customer's construction of tangible property. The Company recognizes revenue for fixed-price contracts under the percentage-of-completion method based generally on the proportion of total direct labor costs incurred to total estimated direct labor costs. When total estimated costs indicate a loss, the Company will recognize the full amount of that loss immediately. Permanent Placement Services - These services include the search for and recruitment of candidates for employment with the Company’s customers. Generally, the Company performs permanent placement services on a non-exclusive, contingency basis. Revenue is recognized only after successfully placing a recommended candidate. Franchise Royalties - MRI’s rights to franchise royalties are governed by the provisions of its franchise contracts. Under the franchise contracts, the franchisees remit to the Company a contractual percentage of fees collected from their customers. The Company records franchise royalty revenue as fees are collected by the franchisee and they become a receivable from the franchisee. Franchise Fees - The Company recognizes fees related to sales of new MRI franchises and master franchise agreements when the Company has substantially fulfilled its requirements under the respective franchise agreement.
Off-Balance Sheet Risk	Off-Balance Sheet Risk - The Company is exposed to risks associated with fluctuations in foreign currency exchange rates because the transactions of its foreign operations are primarily denominated in Canadian dollars. Exchange rate fluctuations impact the U.S. dollar value of reported earnings derived from these foreign operations as well as the Company’s investment in the net assets related to these foreign operations.
Foreign Currency	Foreign Currency - Foreign subsidiaries of the Company use local currency as the functional currency. Net assets are translated at year-end exchange rates while revenue and expenses are translated at average monthly exchange rates. Adjustments resulting from these translations are reflected in “Accumulated other comprehensive loss” in the equity section of the consolidated balance sheets. Gains and losses arising from foreign currency transactions are reflected in “Other income (expense), net” in the consolidated statements of operations.
Concentrations of Credit Risk	Concentrations of Credit Risk - The Company’s principal asset is its accounts receivable. Substantially all of the Company’s customers are provided trade credit. The Company’s customers are primarily large and mid-sized organizations. The Company performs ongoing credit evaluations of its customers and maintains allowances for potential credit losses. The Company considers a number of factors in determining the allowance for doubtful accounts receivable, including an assessment of customer-specific information, the Company’s historical experience, the age of the receivable and current market and economic conditions.
Income Taxes	Income Taxes - The Company accounts for income taxes using the asset and liability method. Under this method, income taxes are provided for amounts currently payable and for amounts deferred as tax assets and liabilities based on differences between the financial statement carrying amounts and tax basis of its assets and liabilities. In establishing its deferred income tax assets and liabilities, the Company makes judgments and interpretations based on the enacted tax laws and published tax guidance. The Company records deferred tax assets and liabilities and evaluates the need for valuation allowances to reduce the deferred tax assets to realizable amounts. The likelihood of a material change in the Company’s expected realization of these assets is dependent on future taxable income, its ability to use tax credit carry forwards and carry backs, final tax settlements and the effectiveness of its tax planning strategies in the various tax jurisdictions in which it operates. The Company recognizes the effect of income tax positions only if those positions are more likely than not to be sustained. Recognized income tax positions are measured at the largest amount that is greater than 50% likely to be realized. Changes in recognition or measurement are reflected in the period in which the change in judgment occurs. See Note 10—Income Taxes.
Cash and Cash Equivalents	Cash and Cash Equivalents - Cash equivalents include highly liquid investments that mature within 90 days from the date of investment. The Company funds its disbursement accounts daily as checks are presented for payment. Book overdrafts represent outstanding checks that have not been presented for payment, net of cash in accounts with the right of offset. Book overdrafts are reported in “Accounts payable” in the consolidated balance sheets and the change in book overdrafts are reported in financing activities in the consolidated statement of cash flows.
Fair Value of Financial Instruments	Fair Value of Financial Instruments - The net carrying amounts of cash and cash equivalents, accounts receivable, accounts payable and credit facilities approximate their fair value due to the short-term nature of these instruments as well as the variable interest rate for short-term borrowings. For financial assets and liabilities measured at fair value on a recurring basis, fair value is the price the Company would receive to sell an asset or pay to transfer a liability in an orderly transaction with a market participant at the measurement date. A three-level fair value hierarchy prioritizes the inputs used to measure fair value as follows: Level 1—quoted prices in active markets for identical instruments; Level 2—quoted prices in active markets for similar instruments, quoted prices for identical instruments in markets that are not active, or other inputs that are observable or can be corroborated by observable data for substantially the full term of the instrument; and Level 3—significant inputs to the valuation model are unobservable.
Property and Equipment	Property and Equipment - Property and equipment are recorded at cost. Depreciation expense for financial reporting purposes is computed using the straight-line method over the following useful lives: Computer equipment 4 years Equipment and furniture 4-10 years Software 4-7 years Leasehold improvements Shorter of lease term or useful life
Goodwill and Other Intangible Assets	Goodwill and Other Intangible Assets - Goodwill represents the excess of the purchase price over the estimated fair market value of identifiable net assets at the date of acquisition in a business combination. Other intangible assets are identifiable assets that lack physical substance, which are acquired as part of a business combination or other transaction. Intangible assets with definite lives are amortized over their useful lives, generally on a straight-line basis. Goodwill and other intangible assets with indefinite lives are not amortized and are tested for impairment at least annually. The Company performs its annual assessment for impairment of goodwill and other indefinite-lived intangible assets as of July 1 of each fiscal year, or whenever events occur or circumstances indicate that it is more likely than not that the fair value of a reporting unit or indefinite-lived intangible asset is below its carrying value. The Company has the option to perform a qualitative assessment for impairment of its goodwill and indefinite-lived intangible assets to determine if it is more likely than not that the fair value of a reporting unit or indefinite-lived intangible asset is below its carrying value. If the Company determines based on a qualitative assessment that it is more likely than not that the fair value of a reporting unit or indefinite-lived intangible asset is greater than its carrying value, then it would not be required to perform the two-step quantitative impairment test described below. If necessary, the Company will perform a quantitative assessment for impairment of its goodwill and indefinite-lived intangible assets using the two-step approach. The first step of the quantitative impairment test requires that the Company determine the fair value of each reporting unit and then compare that fair value to the reporting unit’s carrying amount. The Company uses the income approach to determine the fair value of its reporting units. The Company applies a valuation technique consistent with the income approach to measure the fair value of its indefinite-lived intangible assets. The income approach is based on the present value of projected cash flows for each reporting unit. The income approach requires significant judgment, including estimating projected cash flows, weighted-average cost of capital (WACC) and terminal values. The projected cash flows are based on the Company’s best estimates of future economic and market conditions, including growth rates, estimated earnings and cash expenditures. The fair value of each reporting unit is calculated by discounting cash flow projections by an estimated WACC derived based on a similar market participant's capital structure and the Company's inherent risk profile. The second step of the quantitative impairment test is performed if the first step indicates that impairment exists. The second step of the impairment assessment involves allocating the reporting unit’s fair value to all of its recognized and unrecognized assets and liabilities in order to determine the implied fair value of the reporting unit’s goodwill and intangible assets as of the assessment date. The implied fair value of the reporting unit’s goodwill and other intangible assets is then compared to the carrying amount of goodwill and other intangible assets to quantify an impairment charge as of the assessment date.
Long-Lived Assets	Long-Lived Assets - The Company evaluates long-lived assets and intangible assets with definite lives for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. When it is probable that undiscounted future cash flows will not be sufficient to recover an asset’s carrying amount, the asset is written down to its fair value. Assets to be disposed of by sale are reported at the lower of the carrying amount or fair value less cost to sell.
Leases	Leases - The Company leases office facilities and equipment under operating leases. For significant lease agreements that provide for escalating rent payments or free-rent occupancy periods, the Company recognizes rent expense on a straight-line basis over the non-cancelable lease term. The lease term commences on the date when all conditions precedent to the Company’s obligation to pay rent are satisfied. Deferred rent is included in “Other accrued expenses and other current liabilities” and "Other non-current liabilities" in the consolidated balance sheets. The Company records significant tenant improvement allowances as deferred rent, which is amortized over the term of the lease as a reduction to rent expense. Leasehold improvements associated with the tenant improvement allowance is included in "Property and equipment, net" in the consolidated balance sheets.
Stock-Based Compensation	Share-Based Compensation - The Company accounts for share-based compensation based on the fair value of the award at the date of grant for equity-classified awards or as re-measured each reporting date for liability-classified awards until such awards no longer remain outstanding. The Company estimates the fair value of awards of equity share options or similar awards using option-pricing models, including the Black-Scholes and Monte Carlo simulation models, and recognizes this value as compensation expense over the requisite service period, net of estimated forfeitures.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2014-09 (Topic 606) Revenue from Contracts with Customers (ASU 2014-09). ASU 2014-09 supersedes the revenue recognition requirements in Topic 605, Revenue Recognition, and most industry-specific revenue guidance in addition to some cost guidance. ASU 2014-09 establishes a five-step model under the core principle that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The Company may apply this guidance using either a full retrospective approach, subject to certain practical expedients, or a modified retrospective approach with a cumulative effect adjustment as of the date of initial application. On July 9, 2015, the FASB approved a one-year deferral of the effective date that allows the Company to defer the effective date to January 1, 2018 but still permit the Company to adopt the standard as of the original January 1, 2017 effective date. In 2016, the FASB issued two amendments that are effective as of the effective date selected for the original standard. The Company has begun to evaluate the impact that adoption of this guidance will have on its consolidated financial statements but has not completed the evaluation and implementation process. The Company has not yet selected a transition method but has determined that it will utilize the deferred effective date of January 1, 2018 to adopt the standard. In February 2015, the FASB issued ASU No. 2015-02, Consolidation (Topic 810): Amendments to the Consolidation Analysis (ASU 2015-02). The standard changes the way reporting enterprises evaluate whether (a) they should consolidate limited partnerships and similar entities, (b) fees paid to a decision maker or service provider are variable interests in a variable interest entity (VIE), and (c) variable interests in a VIE held by related parties of the reporting enterprise require the reporting enterprise to consolidate the VIE. The Company adopted ASU 2015-02 during the first quarter of 2016, which adoption did not have a material impact on its consolidated financial statements. In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842), which supersedes ASC 840, Leases (ASU 2016-02). ASU 2016-02 requires lessees to recognize a right-of-use asset and lease liability for all leases with terms of more than 12 months. Lessees are permitted to make an accounting policy election to not recognize the asset and liability for leases with a term of twelve months or less. ASU 2016-02 does not significantly change the lessees’ recognition, measurement and presentation of expenses and cash flows from the previous accounting standard. Lessors’ accounting is largely unchanged from the previous accounting standard. In addition, ASU 2016-02 expands the disclosure requirements of lease arrangements. Lessees and lessors will use a modified retrospective transition approach. The guidance is effective for the Company beginning January 1, 2019. Early adoption is permitted. The Company has not determined the impact that adoption of this guidance will have on its consolidated financial statements. In March 2016, the FASB issued ASU No. 2016-09, Compensation—Stock Compensation (Topic 718) (ASU 2016-09). ASU 2016-09 makes several modifications to Topic 718 related to the accounting for forfeitures, employer tax withholding on share-based compensation and the financial statement presentation of excess tax benefits or deficiencies. ASU 2016-09 also clarifies the statement of cash flows presentation for certain components of share-based awards. The standard is effective for interim and annual reporting periods beginning after December 15, 2016, although early adoption is permitted. The Company adopted ASU 2016-09 on a prospective basis during the first quarter of 2016, which adoption did not have a material impact on its consolidated financial statements. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (ASU 2016-13). ASU 2016-13 changes the methodology for measuring credit losses on financial instruments and the timing of when such losses are recorded. The standard is effective for interim and annual reporting periods beginning after December 15, 2019. Early adoption is permitted for interim and annual reporting periods beginning after December 15, 2018. The Company has not determined the impact that adoption of this guidance will have on its consolidated financial statements. In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 320): Classification of Certain Cash Receipts and Cash Payments (ASU 2016-15). ASU 2016-15 clarifies how certain cash receipts and payments should be presented in the statement of cash flows. The standard is effective for interim and annual reporting periods beginning after December 15, 2017. Early adoption is permitted for interim and annual reporting periods with retrospective application for all periods presented. The Company has not determined the impact that adoption of this guidance will have on its consolidated financial statements.