SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	9 Months Ended
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	Sep. 30, 2015
Accounting Policies [Abstract]
Nature of Operations	EPAM is a global leader in software product development and engineering solutions, servicing clients in over 20 countries across North America, Europe, Asia and Australia. The Company serves global clients in various industries, including Independent Software Vendors (“ISVs”) and technology, banking and financial services, business information and media, travel and hospitality and Life Sciences and Healthcare. The Company is incorporated in Delaware with headquarters in Newtown, PA, with multiple delivery centers located in Belarus, Ukraine, Russia, Hungary, Kazakhstan, Bulgaria, China, Armenia, Poland, Mexico and Austria, and client management locations in the United States, Canada, the United Kingdom, Germany, Sweden, Switzerland, Netherlands, Russia, Kazakhstan, Singapore, China, Hong Kong and Australia.
Basis of Presentation	Basis of Presentation —The accompanying unaudited condensed consolidated financial statements ("financial statements") of EPAM Systems, Inc. (the “Company” or “EPAM”) have been prepared in accordance with generally accepted accounting principles in the United States ("GAAP") and Article 10 of Regulation S-X under the Securities Exchange Act of 1934, as amended. The condensed consolidated financial statements include the financial statements of EPAM Systems, Inc. and its subsidiaries with all intercompany balances and transactions eliminated. These unaudited condensed consolidated financial statements and accompanying notes should be read in conjunction with the Company’s audited consolidated financial statements and the notes thereto for the year ended December 31, 2014 included in its Annual Report on Form 10-K.
Use of Estimates	The preparation of these condensed consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in these condensed consolidated financial statements and accompanying notes. Actual results could differ from those estimates, and such differences may be material to the condensed consolidated financial statements. Additionally, operating results for the interim periods are not necessarily indicative of results that may be expected to occur for the entire year.
Revenue Recognition	Revenue Recognition — The Company recognizes revenue when the following criteria are met: (1) persuasive evidence of an arrangement exists; (2) delivery has occurred; (3) the sales price is fixed or determinable; and (4) collectability is reasonably assured. Determining whether and when some of these criteria have been satisfied often involves assumptions and judgments that can have a significant impact on the timing and amount of revenue reported. The Company derives its revenues from a variety of service offerings, which represent specific competencies of its IT professionals. Contracts for these services have different terms and conditions based on the scope, deliverables, and complexity of the engagement, which require management to make judgments and estimates in determining appropriate revenue recognition pattern. Fees for these contracts may be in the form of time-and-materials or fixed-price arrangements. If there is an uncertainty about the project completion or receipt of payment for the consulting services, revenue is deferred until the uncertainty is sufficiently resolved. At the time revenue is recognized, the Company provides for any contractual deductions and reduces the revenue accordingly. The Company reports gross reimbursable “out-of-pocket” expenses incurred as both revenues and cost of revenues in the condensed consolidated statements of income and comprehensive income. The Company defers amounts billed to its clients for revenues not yet earned. Such amounts are anticipated to be recorded as revenues when services are performed in subsequent periods. Unbilled revenue is recorded when services have been provided but billed subsequent to the period end in accordance with the contract terms.
Fair Value of Financial Instruments	Fair Value of Financial Instruments — The Company makes assumptions about fair values of its financial assets and liabilities in accordance with the Financial Accounting Standards Board (FASB) Accounting Standards Codification (ASC) Topic 820, "Fair Value Measurement," and utilizes the following fair value hierarchy in determining inputs used for valuation: Level 1 — Quoted prices for identical assets or liabilities in active markets. Level 2 — Inputs other than quoted prices within Level 1 that are observable either directly or indirectly, including quoted prices in markets that are not active, quoted prices in active markets for similar assets or liabilities, and observable inputs other than quoted prices such as interest rates or yield curves. Level 3 — Unobservable inputs reflecting our view about the assumptions that market participants would use in pricing the asset or liability. Where the fair values of financial assets and liabilities recorded in the condensed consolidated balance sheets cannot be derived from an active market, they are determined using a variety of valuation techniques. These valuation techniques include a net present value technique, comparison to similar instruments with market observable inputs, options pricing models and other relevant valuation models. To the extent possible, observable market data is used as inputs into these models but when it is not feasible, a degree of judgment is required to establish fair values. Financial Assets and Liabilities Measured At Fair Value on a Recurring Basis The Company's contingent liabilities measured at fair value on a recurring basis are comprised of performance-based awards issued to certain former owners of the acquired businesses in exchange for future services. Contingent liabilities are valued using significant inputs that are not observable in the market, which are defined as Level 3 inputs according to fair value measurement accounting. The Company estimates the fair value of contingent liabilities based on certain performance milestones of the acquired businesses and estimated probabilities of achievement, then discounts the liabilities to present value using the Company’s cost of debt for the cash component of contingent consideration, and risk free rate for the stock component of a contractual contingency. The Company believes its estimates and assumptions are reasonable, however, there is significant judgment involved. Changes in the fair value of contingent consideration liabilities primarily result from changes in the timing and amount of specific milestone estimates and changes in probability assumptions with respect to the likelihood of achieving the various earnout criteria. These changes could cause a material impact to, and volatility in the Company’s operating results. Additionally, during the third quarter of 2015, the Company entered into derivative financial instruments to manage exposure to fluctuations in certain foreign currencies. For accounting purposes, these foreign currency option and forward contracts are not designated as hedges, as defined under FASB ASC Topic 815, "Derivatives and Hedging," and all changes in their fair value are reported within foreign exchange gain/(loss) line of the unaudited condensed consolidated statements of income and comprehensive income. The Company measures these foreign currency derivative contracts at fair value on a recurring basis utilizing Level 2 inputs. Financial Assets and Liabilities Measured At Fair Value on a Non-Recurring Basis The amounts of the Company’s financial assets and liabilities, with the exceptions of employee housing loans and other employee loans described further herein, approximate fair value because of their short-term maturities. See Note 4 for disclosures related to fair value. Employee Loans — The Company issues employee housing loans in Belarus and relocation loans to assist employees with relocation needs in connection with intra-company transfers. There are no loans issued to principal officers, directors, and their affiliates. On a quarterly basis, the Company reviews the aging of its loan portfolio to evaluate information about the ability of employees to service their debt, including historical payment experience, reasons for payment delays and shortfalls, if any, as well as probability of collecting scheduled principal and interest payments based on the knowledge of individual borrowers, among other factors. Since the initiation of the loan program there have not been material past due or non-accrual employee loans or write offs related to loan losses and, therefore, the Company determined that no allowance for loan losses is required. Employee Housing Loans — In the third quarter of 2012, the Board of Directors of the Company approved the Employee Housing Program (the “Housing Program”), which assists employees with purchasing housing in Belarus in a form of a loan. The Housing Program was designed to be a retention mechanism for the Company’s employees in Belarus and is available to full-time qualified employees who have been with the Company for at least 3 years. The aggregate maximum lending limit of the program is $10,000, with individual loans not exceeding $50. The housing is sold directly to employees by independent third parties. Loans issued under the Housing Program are denominated in U.S. dollars with a 5-year term and an interest rate of 7.5%. The housing loans were classified as Level 3 measurements within the fair value hierarchy because they were valued using significant unobservable inputs. The estimated fair value of these housing loans upon initial recognition was computed by projecting the future contractual cash flows to be received from the loans and discounting those projected net cash flows to a present value, which is the estimated fair value (the “Income Approach”). In applying the Income Approach, the Company analyzed similar loans offered by third-party financial institutions in Belarusian rubles and adjusted the interest rates charged on such loans to exclude the effects of underlying economic factors, such as inflation and currency devaluation. The Company also assessed the probability of future defaults and associated cash flows impact. In addition, the Company separately analyzed the rate of return that market participants in Belarus would require when investing in unsecured U.S. dollar-denominated government bonds with similar maturities (a “risk-free rate”) and evaluated a risk premium component to compensate the market participants for the credit and liquidity risks inherent in the loans’ cash flows. As a result of the analysis performed, the Company determined the carrying values of the housing loans issued during the nine months ended September 30, 2015 approximated their fair values upon initial recognition. The Company also estimated the fair values of the housing loans that were outstanding as of September 30, 2015 using the inputs noted above and determined their fair values approximated the carrying values as of that date. Employee Loans, Other — The Company issues short-term, non-interest bearing relocation loans to employees that relocated within the company. Due to the short term of employee loans and high certainty of repayment, their carrying amount is a reasonable estimate of their fair value.
Business Combinations	Business Combinations — The Company accounts for its business combinations using the acquisition accounting method, which requires it to determine the fair value of net assets acquired and the related goodwill and other intangible assets in accordance with the FASB ASC Topic 805, "Business Combinations." The Company identifies and attributes fair values and estimated lives to the intangible assets acquired and allocates the total cost of an acquisition to the underlying net assets based on their respective estimated fair values. Determining the fair value of assets acquired and liabilities assumed requires management’s judgment and involves the use of significant estimates, including projections of future cash inflows and outflows, discount rates, asset lives and market multiples. There are different valuation models for each component, the selection of which requires considerable judgment. These determinations will affect the amount of amortization expense recognized in future periods. The Company bases its fair value estimates on assumptions it believes are reasonable, but recognizes that the assumptions are inherently uncertain. If initial accounting for the business combination has not been completed by the end of the reporting period in which the business combination occurs, provisional amounts are reported for which the accounting is incomplete, with retrospective adjustment made to such provisional amounts during the measurement period to present new information about facts and circumstances that existed as of the acquisition date. Once the measurement period ends, and in no case beyond one year from the acquisition date, revisions of the accounting for the business combination are recorded in earnings. All acquisition-related costs, other than the costs to issue debt or equity securities, are accounted for as expenses in the period in which they are incurred. Changes in fair value of contingent consideration arrangements that are not measurement period adjustments are recognized in earnings. Payments to settle contingent consideration, if any, are reflected in cash flows from financing activities and the changes in fair value are reflected in cash flows from operating activities in the Company’s condensed consolidated statements of cash flows. The Company’s acquisitions usually do not have significant amounts of tangible assets, as the principal assets typically acquired are customer relationships, trade names, non-competition agreements, and workforce. As a result, a substantial portion of the purchase price is allocated to goodwill and other intangible assets.
Goodwill and Other Intangible Assets	Goodwill and Other Intangible Assets — Goodwill and intangible assets that have indefinite useful lives are treated consistently with FASB ASC 350, "Intangibles - Goodwill and Other." They are tested annually for impairment and are not amortized. Intangible assets that have finite useful lives are amortized over their estimated useful lives on a straight-line basis. When facts and circumstances indicate potential impairment of amortizable intangible assets, the Company evaluates the recoverability of the asset’s carrying value, using estimates of future cash flows that utilize a discount rate determined by its management to be commensurate with the risk inherent in the Company’s business model over the remaining asset life. The estimates of future cash flows attributable to intangible assets require significant judgment based on the Company’s historical and anticipated results. Any impairment loss is measured by the excess of carrying value over fair value.
Stock-based Compensation	Stock-Based Compensation — The Company recognizes the cost of its share-based incentive awards based on the fair value of the award at the date of grant net of estimated forfeitures. The cost is expensed evenly over the service period. The service period is the period over which the employee performs the related services, which is normally the same as the vesting period. Over time, the forfeiture assumption is adjusted to the actual forfeiture rate and such change may affect the timing of the total amount of expense recognized over the vesting period. Equity-based awards that do not require future service are expensed immediately. Equity-based awards that do not meet the criteria for equity classification are recorded as liabilities and adjusted to fair value at the end of each reporting period.
Off-Balance Sheet Financial Instruments	Off-Balance Sheet Financial Instruments — The Company uses the FASB ASC Topic 825, "Financial Instruments." to identify and disclose off-balance sheet financial instruments, which include credit instruments, such as commitments to make employee loans and related guarantees, standby letters of credit and certain guarantees issued under customer contracts. The face amount for these items represents the exposure to loss, before considering available collateral or the borrower’s ability to repay. Loss contingencies arising from off-balance sheet financial instruments are recorded as liabilities when the likelihood of loss is probable and an amount or range of loss can be reasonably estimated. The Company does not believe such matters exists that will have a material effect on the condensed consolidated financial statements.