Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2017
Accounting Policies [Abstract]
Basis of Presentation and Consolidation	Basis of Presentation and Consolidation The consolidated financial statements include the accounts of Computer Task Group, Incorporated, and its subsidiaries (the Company or CTG), located primarily in North America, Western Europe, and India. There are no unconsolidated entities, or off-balance sheet arrangements other than certain guarantees supporting office leases and the performance under government contracts in the Company's European operations. All inter-company accounts have been eliminated. Management of the Company has made a number of estimates and assumptions relating to the reporting of assets and liabilities and the disclosure of contingent assets and liabilities to prepare these consolidated financial statements in conformity with U.S. generally accepted accounting principles. Such estimates primarily relate to the valuation allowances for deferred tax assets, actuarial assumptions including discount rates and expected rates of return, as applicable, for the Company’s defined benefit plans, the allowance for doubtful accounts receivable, assumptions underlying stock option valuation, investment valuation, estimates of progress toward completion and direct profit or loss on contracts, legal matters, and other contingencies. The current economic environments in the United States, Canada, Western Europe, and India where the Company has operations have increased the degree of uncertainty inherent in these estimates and assumptions. Actual results could differ from those estimates. The Company operates in one industry segment, providing IT services to its clients. These services include IT Solutions and IT and other Staffing. CTG provides these services to all of the markets that it serves. The services provided typically encompass the IT business solution life cycle, including phases for planning, developing, implementing, managing, and ultimately maintaining the IT solution. A typical client is an organization with large, complex information and data processing requirements. The Company provides administrative or warehouse employees to clients from time to time to supplement the IT resources we place at those clients. The Company promotes a significant portion of its services through five vertical market focus areas: technology service providers, manufacturing, healthcare (which includes services provided to healthcare providers, health insurers, and life sciences companies), financial services, and energy. The Company focuses on these five vertical areas as it believes that these areas are either higher growth markets than the general IT services market and the general economy, or are areas that provide greater potential for the Company’s growth due to the size of the vertical market. The remainder of CTG’s revenue is derived from general markets.
Revenue and Cost Recognition	Revenue and Cost Recognition The Company recognizes revenue when persuasive evidence of an arrangement exists, when the services have been rendered, when the price is determinable, and when collectibility of the amounts due is reasonably assured. For time-and-material contracts, revenue is recognized as hours are incurred and costs are expended. For contracts with periodic billing schedules, primarily monthly, revenue is recognized as services are rendered to the client. Revenue for fixed-price contracts is recognized per the proportional method of accounting using an input-based approach. On a given project, actual salary and indirect labor costs incurred are measured and compared against the total estimated costs of such items at the completion of the project. Revenue is recognized based upon the percentage-of-completion calculation of total incurred costs to total estimated costs. The Company infrequently works on fixed-price projects that include significant amounts of material or other non-labor related costs which could distort the percent complete within a percentage-of-completion calculation. The Company’s estimate of the total labor costs it expects to incur over the term of the contract is based on the nature of the project and our past experience on similar projects, and includes management judgments and estimates which affect the amount of revenue recognized on fixed-price contracts in any accounting period. Loss on contracts, if any, are recorded at the time it is determined a loss exists on a project.
Fair Value	Fair Value Fair value is defined as the exchange price that would be received for an asset or paid for a liability in the principal or most advantageous market for the asset or liability, in an orderly transaction between market participants. The Company utilizes a fair value hierarchy for its assets and liabilities, as applicable, based upon three levels of input, which are: Level 1—quoted prices in active markets for identical assets or liabilities (observable) Level 2—inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities, quoted prices in inactive markets, or other inputs that are observable or can be supported by observable market data for essentially the full term of the asset or liability (observable) Level 3—unobservable inputs that are supported by little or no market activity, but are significant to determining the fair value of the asset or liability (unobservable) At December 31, 2017 and 2016, the carrying amounts of the Company’s cash of $11.2 million and $9.4 million, respectively, approximated fair value. The Company is also allowed to elect an irrevocable option to measure, on a contract by contract basis, specific financial instruments and certain other items that are currently not being measured at fair value. The Company did not elect to apply the fair value provisions of this standard for any specific contracts during the years ended December 31, 2017 and 2016.
Life Insurance Policies	Life Insurance Policies The Company has purchased life insurance on the lives of a number of former employees who are plan participants in the non-qualified defined benefit Executive Supplemental Benefit Plan. In total, there are policies on approximately 20 individuals, whose average age is 74 years old. These policies have generated cash surrender value, and the Company, prior to 2015, had taken loans against the policies. At December 31, 2017 and 2016, these insurance policies had a gross cash surrender value of $31.5 million and $30.1 million, respectively, and was included on the consolidated balance sheet as “Cash surrender value of life insurance.” There were no outstanding loans against these policies in 2017 and 2016. At December 31, 2017 and 2016 the total death benefit for the remaining policies was approximately $42.2 million and $41.4 million, respectively. Currently, upon the death of all of the plan participants, the Company would expect to receive approximately $41.6 million, and under current tax regulations, would record a non-taxable gain of approximately $10.1 million. Two former employees covered by this life insurance passed away, one in the 2017 fourth quarter and the other in the 2015 fourth quarter. The Company recorded non-taxable gains of approximately $0.4 million and $0.2 million in the respective quarters. The Company expects to receive $1.1 million in the 2018 first quarter for the 2017 death and received approximately $0.4 million in the 2016 first quarter for the 2015 death.
Taxes Collected from Clients	Taxes Collected from Clients In instances where the Company collects taxes from its clients for remittance to governmental authorities, primarily in its European operations, revenue and expenses are not presented on a gross basis in the consolidated financial statements as such taxes are recorded in the Company's accounts on a net basis.
Cash and Cash Equivalents, and Cash Overdrafts	Cash and Cash Equivalents, and Cash Overdrafts For purposes of the statement of cash flows, cash and cash equivalents are defined as cash on hand, demand deposits, and short-term, highly liquid investments with a maturity of three months or less. As the Company does not fund its bank accounts for the checks it has written until the checks are presented to the bank for payment, the "change in cash overdraft, net" line item as presented on the consolidated statement of cash flows represents the increase or decrease in outstanding checks for a given period.
Trade Accounts Receivable	Trade Accounts Receivable Trade accounts receivable balances are received on average approximately 86 days from the date of invoice. Generally, the Company does not work on any projects where amounts due are expected to be received greater than one year from the date of the invoice. Accordingly, the recorded book value for the Company’s accounts receivable equals fair value. Outstanding trade accounts receivable are generally considered past due when they remain unpaid after the contractual due date has passed. An allowance for doubtful accounts receivable (allowance) is established using management’s judgment. Specific identification of balances that are significantly past due and where client payments have not been recently received are generally added to the allowance unless the Company has direct knowledge that the client intends to make payment. Additionally, any balances which relate to a client that has declared bankruptcy or ceased its business operations are added to the allowance at the amount not expected to be received.
Property, Equipment and Capitalized Software Costs	Property, Equipment and Capitalized Software Costs Property and equipment are generally stated at historical cost less accumulated depreciation. Depreciation is computed using the straight-line method based on estimated useful lives of one year to 30 years, and begins after an asset has been placed into service. Leasehold improvements are generally depreciated over the shorter of the term of the lease or the useful life of the improvement. The cost of property or equipment sold or otherwise disposed of, along with related accumulated depreciation, is eliminated from the accounts, and the resulting gain or loss, if any, is reflected in current earnings. Maintenance and repairs are charged to expense when incurred, while significant improvements to existing assets are capitalized. As of December 31, 2017 and 2016, the Company had capitalized costs relating to software projects developed for internal use. Amortization periods for these projects range from two to five years, and begin when the software, or enhancements thereto, is available for its intended use. Amortization periods are evaluated annually for propriety.
Impairment of Long-Lived Assets and Long-Lived Assets to Be Disposed Of	Impairment of Long-Lived Assets and Long-Lived Assets to Be Disposed Of Long-lived assets are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. When such circumstances exist, the recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to future cash flows expected to be generated by the asset. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the assets exceeds the fair value of the assets. Assets to be disposed of by sale, if any, are reported at the lower of the carrying amount or fair value less costs to sell.
Leases	Leases The Company is obligated under a number of short and long-term operating leases, primarily for the rental of office space, office equipment, and for automobiles in our European operations. In instances where the Company has negotiated leases that contain rent holidays or escalation clauses, the expense for those leases is recognized monthly on a straight-line basis over the term of the lease.
Goodwill	Goodwill The goodwill recorded on the Company's condensed consolidated balance sheet at December 31, 2015 related to CTG’s Healthcare Solutions (CTGHS) reporting unit. In accordance with current accounting guidance for “Intangibles - Goodwill and Other,” the Company performs goodwill impairment testing at least annually (in the Company’s fourth quarter), unless indicators of impairment exist in interim periods. The Company uses the two-step approach to test goodwill for potential impairment. Step One compares the estimated fair value of a reporting unit with goodwill to its carrying value. If the carrying value exceeds the estimated fair value, Step Two must be performed. Step Two compares the carrying value of the reporting unit to the fair value of all of the assets and liabilities of the reporting unit (including any unrecognized intangibles) as if the reporting unit was acquired in a business combination. If the carrying amount of a reporting unit’s goodwill exceeds the implied fair value of its goodwill, an impairment loss is recognized in an amount equal to the excess. During the 2016 first quarter, the Company determined that a goodwill impairment indicator existed which required an interim impairment analysis. This impairment indicator was a significant and sustained decrease in the Company’s overall market capitalization, as the Company’s stock price in the 2016 first quarter fell by as much as 29% from its value at December 31, 2015. As a result of this indicator, the Company conducted an interim analysis of CTGHS to determine if an impairment existed. In performing the assessment, the Company estimated the fair value of CTGHS based on a combination of the income and market approaches. The income approach uses a discounted cash flow (DCF) method which utilizes the present value of expected future cash flows to estimate fair value of the reporting unit. The future cash flows for CTGHS was projected based on estimates of future revenue, operating income and other factors such as working capital and capital expenditures and a discount rate used in the present value calculation. As part of the projections, the Company took into account expected industry and market conditions for the healthcare industry, as well as trends currently affecting CTGHS. The market approach utilizes multiples of revenue and earnings before interest expense, taxes, depreciation and amortization (EBITDA) to estimate the fair value of the reporting unit. The market multiples used for CTGHS were based on competitor industry data, along with the market multiples for the Company and other factors. The Company also completed a comparison of its overall market capitalization to the market value of CTGHS and the Company’s other non-reporting business units. Based upon the analysis performed, the Company determined that the fair value of CTGHS was less than its carrying value, which required the Company to perform a Step Two goodwill impairment test. As a result of the first quarter Step Two analysis, the Company determined the implied fair value of its goodwill balance was below the carrying value. Accordingly, the Company recorded a non-tax deductible goodwill impairment charge of $21.5 million to reduce the value of its goodwill balance to the implied fair value. During the 2016 third quarter, the Company again determined that goodwill impairment indicators existed which required an interim impairment analysis. These impairment indicators were the unexpected decline in the revenue and profits of the CTGHS business unit, the resignation of both the sales leader (who was the Company’s former CEO) and delivery leader of CTGHS in the 2016 third quarter, effectively leaving the business unit without executive leadership, and a continued decrease in the Company’s overall market capitalization. As a result of these indicators, the Company conducted an interim analysis of CTGHS to determine if an impairment existed. In performing the assessment, the Company again performed the procedures it had previously performed in the 2016 first quarter, as detailed above. The most significant changes in the Company’s Step One analysis from the first quarter to the third quarter were reductions in the Company’s estimates of future revenue and operating income based upon the unexpected negative trends experienced in the third quarter, as well as the resulting reductions in the revenue and EBITDA market multiples that correlate to the decline in our overall market capitalization. Based upon the analysis performed, the Company determined that the fair value of CTGHS was less than its carrying value, which required the Company to perform a Step Two goodwill impairment test. As a result of the third quarter Step Two analysis, the Company determined the implied fair value of its goodwill balance was below the carrying value. Accordingly, the Company recorded a non-tax deductible goodwill impairment charge in the 2016 third quarter of $15.8 million which reduced the value of its goodwill balance to the implied fair value, or $0.0 as of September 30, 2016.
Income Taxes	Income Taxes On December 22, 2017, the U.S. government enacted comprehensive tax legislation commonly referred to as the Tax Cuts and Jobs Act (the “Tax Act”), The Tax Act makes broad and complex changes to the U.S. tax code, including, but not limited to, (1) reducing the U.S. federal corporate tax rate from 35 percent to 21 percent; (2) requiring companies to pay a one-time transition tax on certain unrepatriated earnings of foreign subsidiaries; (3) generally eliminating U.S. federal income taxes on dividends from foreign subsidiaries; (4) requiring a current inclusion in U.S. federal taxable income of certain earnings of controlled foreign corporations; (5) eliminating the corporate alternative minimum tax (AMT) and changing how existing AMT credits can be realized; (6) creating the base erosion anti-abuse tax (BEAT), a new minimum tax; (7) creating a new limitation on deductible interest expense; and (8) changing rules related to uses and limitations of net operating loss carryforwards created in tax years beginning after December 31, 2017. Accounting Standards Codification (ASC) 740, Income Taxes, requires companies to recognize the effect of the tax law changes in the period of enactment. However, the SEC staff issued Staff Accounting Bulletin (SAB) 118, which allows companies to record provisional amounts during a measurement period that is similar to the measurement period used when accounting for business combinations. The Company has recorded a reasonable estimate when possible and with the understanding that the provisional amount is subject to further adjustments under SAB 118. As a result, the Company has recorded the following provisional amounts in the financial statements, which will be revised, if necessary, as the computations become finalized during the measurement period. Deferred tax assets and liabilities: The Company remeasured certain deferred tax assets and liabilities based on the federal rate at which they are expected to reverse in the future, which is generally 21%. The Company also remeasured the state rate at which certain deferred tax assets and liabilities are expected to reverse in the future associated with the reduction in the future federal benefit from state deferred tax assets and liabilities from 34% to 21%. However, the Company is still analyzing certain aspects of the Act relating to compensation expense and refining its calculations, which could potentially affect the measurement of these balances or potentially give rise to new deferred tax amounts. The provisional amount recorded related to the remeasurement of the Company's deferred tax balance was a tax expense of $1.7 million, including the remeasurement of its federal valuation allowance. Foreign tax effects: The one-time transition tax is based on the Company's total post-1986 earnings and profits (E&P) that were previously deferred from U.S. income taxes. The Company currently estimates there will be no liability for the one-time transition tax for all of its foreign subsidiaries since the accumulated post-1986 earnings is currently estimated to be negative. The Company has not yet completed its calculation of the total post-1986 E&P for these foreign subsidiaries and this amount may change when the Company finalizes the calculation of post-1986 foreign E&P previously deferred from U.S. federal taxation and finalizes the amounts held in cash or other specified assets. The Company has not provided for any additional outside basis difference inherent in its foreign subsidiaries, as these amounts continue to be indefinitely reinvested in foreign operations. The Company has not yet made a policy election with respect to its treatment of potential global intangible low-taxed income (GILTI). Companies can either account for taxes on GILTI as incurred or recognize deferred taxes when basis differences exist that are expected to affect the amount of the GILTI inclusion upon reversal. The Company is still in the process of analyzing the provisions of the Act associated with GILTI and the expected impact of GILTI on the Company in the future. The Company provides for deferred income taxes for the temporary differences between the financial reporting basis and the tax basis of the Company’s assets and liabilities. In assessing the realizability of deferred tax assets, management considers within each tax jurisdiction, whether it is more likely than not that some portion or all of the deferred tax assets will not be realized. Management considers the scheduled reversal of deferred tax liabilities, projected future taxable income, and tax-planning strategies in making this assessment. The Company recognizes, as applicable, accrued interest and penalties related to unrecognized tax benefits (if any) in tax expense. The Company establishes an unrecognized tax benefit based upon the anticipated outcome of tax positions taken for financial statement purposes compared with positions taken on the Company’s tax returns. The Company records the benefit for unrecognized tax benefits only when it is more likely than not that the position will be sustained upon examination by the taxing authorities. The Company reviews its unrecognized tax benefits on a quarterly basis. Such reviews include consideration of factors such as the cause of the action, the degree of probability of an unfavorable outcome, the Company’s ability to estimate the liability, and the timing of the liability and how it will impact the Company’s other tax attributes.
Equity-Based Compensation	Equity-Based Compensation The Company records the fair value of equity-based compensation expense for all equity-based compensation awards granted and recognizes the cost in the Company’s income statement over the periods in which an employee or director is required to provide the services for the award. Compensation cost is not recognized for employees or directors that do not render the requisite services. The Company recognized the expense for equity-based compensation in its 2017, 2016, and 2015 statements of income on a straight-line basis based upon awards that are ultimately expected to vest.
Net Income (Loss) Per Share	Net Income (Loss) Per Share Weighted-average shares represent the average number of issued shares less treasury shares and shares held in the Stock Trusts, and for the basic EPS calculations, unvested restricted stock.
Foreign Currency	Foreign Currency The functional currency of the Company’s foreign subsidiaries is the applicable local currency. The translation of the applicable foreign currencies into U.S. dollars is performed for assets and liabilities using current exchange rates in effect at the balance sheet date, for equity accounts using historical exchange rates, and for revenue and expense activity using the applicable month’s average exchange rates.
Guarantees	Guarantees The Company has a number of guarantees in place in our European operations which support office leases and performance under government projects. These guarantees totaled approximately $1.1 million at both December 31, 2017 and 2016, and generally have expiration dates ranging from March 2018 through April 2020.
Recently Issued Accounting Standards	Recently Issued Accounting Standards In May 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update No. 2014-09, "Revenue from Contracts with Customers (Topic 606)," ("ASU 2014-09"). ASU 2014-09 outlines a new, single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and supersedes most current revenue recognition guidance, including industry-specific guidance. This new revenue recognition model provides a five-step analysis in determining when and how revenue is recognized. The new model will require revenue recognition to depict the transfer of promised goods or services to customers in an amount that reflects the consideration a company expects to receive in exchange for those goods or services. The pronouncement is effective for fiscal years, and interim periods within those years, beginning after December 15, 2017, and early adoption is only permitted in years beginning after December 31, 2016. The Company will apply the new standard using the cumulative effect method and will apply the requirements of the new standard to only projects that are open as of January 1, 2018. The Company currently records approximately 97% of its annual revenue on a time-and-material and progress billing basis, with the remaining 3% recorded under a proportional method of accounting using an inputs based methodology for fixed price projects. For the 97% of the Company’s revenue recorded under the time-and-material method of accounting, excluding the principal and agent considerations described below, the new standard will not change the timing or the amount of revenue that is recorded. The Company has also evaluated the revenue recorded under its fixed price projects to determine if the manner or timing of revenue recognition would change for existing projects. The impact of adopting this new accounting guidance will have an immaterial impact on the timing and amount of revenue recorded under its fixed price projects. When more than one party is involved in providing goods or services to a customer, the standard requires an entity to determine whether it is a principal or an agent in these transactions by evaluating the nature of its promise to the customer. The fundamental premise of the principal and agent determination is the concept of control. The Company had recorded approximately 3% of its consolidated revenue on a net basis during 2017 under current accounting rules. Under the new standard, the Company will report gross revenue and expense for a significant portion of this revenue beginning January 1, 2018. In November 2015, the FASB issued ASU 2015-17, “Balance Sheet Classifications of Deferred Taxes,” which amended accounting guidance related to the presentation of deferred tax liabilities and assets. The amended guidance requires that all deferred tax liabilities and assets be classified as noncurrent on the balance sheet. This guidance was effective for reporting periods beginning after December 15, 2016. Upon adoption of this guidance in the 2017 first quarter, the Company reclassified approximately $0.9 million as of both March 31, 2017 and December 31, 2016 from current to non-current assets. In February 2016, the FASB issued ASU 2016-02, “Leases (Topic 842),” which sets out the principles for the recognition, measurement, presentation and disclosure of leases for both parties to a contract (i.e. lessees and lessors). The new standard requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase by the lessee. This classification will determine whether lease expense is recognized based on an effective interest method or on a straight line basis over the term of the lease, respectively. A lessee is also required to record a right-of-use asset and a lease liability for all leases with a term of greater than 12 months regardless of their classification. Leases with a term of 12 months or less will be accounted for similar to existing guidance for operating leases today. Topic 842 supersedes the previous leases standard, ASC 840, Leases. This guidance is effective for reporting periods beginning after December 15, 2018; however, early adoption is permitted. Entities are required to use a modified retrospective approach for leases that exist or are entered into after the beginning of the earliest comparative period in the financial statements. The Company is currently evaluating the impact that ASU 2016-02 will have on its consolidated financial statements. In March 2016, the FASB issued ASU 2016-09, “Improvements to Employee Share-Based Payment Accounting,” which amended accounting guidance related to seven aspects of the accounting for share-based payments award transactions. This guidance was effective for reporting periods beginning after December 15, 2016. During 2017, the Company recorded approximately $0.3 million of additional tax expense for tax shortfalls that would previously have been recorded to capital in excess of par value. We have adopted this guidance prospectively and prior periods have not been adjusted. Additionally, the Company recorded $0.3 million, $0.4 million, and $0.6 million in 2017, 2016, and 2015, respectively, for taxes remitted for shares withheld from equity-based compensation transaction on the consolidated statements of cash flows in the “cash flows from financing activities” section.
Subsequent Event	Subsequent Event On February 15, 2018, the Company acquired 100% of the equity of Soft Company for approximately $16.8 million. The acquisition was funded using cash on hand and borrowings under the Credit and Security Agreement. Soft Company, located in Paris, France, is an IT consulting company that specializes in providing IT services to finance, insurance, telecom, and media services companies. The acquisition of Soft Company is expected to enable the Company to expand its position in Europe and enhance its service offerings.