NATURE OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES | NATURE OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES EPAM is a leading global provider of digital platform engineering and software development services to clients located around the world, primarily in North America, Europe, Asia and Australia. The Company has expertise in various industries, including software and hi-tech, financial services, media and entertainment, travel and hospitality, retail and distribution and life sciences and healthcare. The Company is incorporated in Delaware with headquarters in Newtown, PA. Principles of Consolidation — The consolidated financial statements include the financial statements of EPAM Systems, Inc. and its subsidiaries. All intercompany balances and transactions have been eliminated. Use of Estimates — The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions. These estimates and assumptions affect reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the financial statements, as well as revenues and expenses during the reporting period. The Company bases its estimates and judgments on historical experience, knowledge of current conditions and its beliefs of what could occur in the future, given available information. Actual results could differ from those estimates, and such differences may be material to the financial statements. Change in Presentation of Certain Financial Information — During the first quarter of 2017, the Company changed the presentation of geographic area information about its consolidated revenues. Historically, information about geographic location of revenues excluded reimbursable expenses and other revenues, which primarily consist of travel and entertainment costs that are chargeable to clients. Effective January 1, 2017, the Company began reporting reimbursable expenses and other revenues based on location of clients to which these costs are chargeable and allocating them to respective geographic locations. These changes did not result in adjustments to previously reported consolidated revenues in the Company’s financial statements and were applied retrospectively effective January 1, 2015. Comparative information for the years ended December 31, 2016 and 2015 follows: Year Ended December 31, 2016 As Reported After Reclassification (in thousands except percentages) United States $ 605,856 52.2 % $ 611,392 52.7 % United Kingdom 174,719 15.1 % 177,194 15.3 % Switzerland 122,399 10.6 % 122,919 10.6 % Canada 58,742 5.1 % 59,189 5.1 % Germany 43,216 3.7 % 43,621 3.8 % Russia 40,866 3.5 % 40,944 3.5 % Sweden 22,945 2.0 % 23,838 2.1 % Hong Kong 20,333 1.8 % 21,010 1.8 % Netherlands 16,762 1.4 % 17,521 1.5 % Belgium 8,505 0.7 % 8,627 0.7 % Ireland 5,152 0.4 % 5,167 0.4 % China 4,445 0.4 % 4,479 0.4 % Italy 3,970 0.3 % 4,052 0.3 % United Arab Emirates 3,486 0.3 % 3,615 0.3 % Other locations 16,215 1.4 % 16,564 1.5 % Reimbursable expenses and other revenues 12,521 1.1 % — — % Total $ 1,160,132 100.0 % $ 1,160,132 100.0 % Year Ended December 31, 2015 As Reported After Reclassification (in thousands except percentages) United States $ 427,433 46.8 % $ 431,992 47.3 % United Kingdom 164,301 18.0 % 166,418 18.2 % Switzerland 111,353 12.2 % 111,686 12.2 % Canada 57,643 6.3 % 58,319 6.4 % Germany 36,089 3.9 % 36,403 4.0 % Russia 36,506 4.0 % 36,585 4.0 % Sweden 10,589 1.2 % 10,775 1.2 % Hong Kong 23,117 2.5 % 23,285 2.5 % Netherlands 9,989 1.1 % 10,373 1.1 % Belgium 7,916 0.9 % 8,113 0.9 % Ireland 5,437 0.6 % 5,536 0.6 % Italy 2,318 0.3 % 2,342 0.3 % China 817 0.1 % 817 0.1 % Other locations 11,109 1.1 % 11,484 1.2 % Reimbursable expenses and other revenues 9,511 1.0 % — — % Total $ 914,128 100.0 % $ 914,128 100.0 % 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 the appropriate revenue recognition. 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 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. The majority of the Company’s revenues ( 90.3% of revenues in 2017 , 88.2% in 2016 and 85.8% in 2015 ) are generated under time-and-material contracts where revenues are recognized as services are performed with the corresponding cost of providing those services reflected as cost of revenues. The majority of such revenues are billed using hourly, daily or monthly rates as actual time is incurred on the project. Revenues from fixed-price contracts ( 8.3% of revenues in 2017 , 10.4% in 2016 and 12.8% in 2015 ) include fixed-price maintenance and support arrangements, which may exceed one year in duration, as well as fixed-price application development arrangements. Revenues from maintenance and support arrangements are generally recognized ratably over the expected service period. Revenues from fixed-price application development arrangements are primarily determined using the proportional performance method. In cases where final acceptance of the product, system, or solution is specified by the client, and the acceptance criteria are not objectively determinable to have been met as the services are provided, revenues are deferred until all acceptance criteria have been met. In the absence of a sufficient basis to measure progress towards completion, revenue is recognized upon receipt of final acceptance from the client. Assumptions, risks and uncertainties inherent in the estimates used in the application of the proportional performance method of accounting could affect the amount of revenues, receivables and deferred revenues at each reporting period. Cost of Revenues (Exclusive of Depreciation and Amortization) — Consists principally of salaries, bonuses, fringe benefits, stock-based compensation expense, project related travel costs and fees for subcontractors that are assigned to client projects. Salaries and other compensation expenses of our revenue generating professionals are reported as cost of revenues regardless of whether the employees are actually performing client services during a given period. Selling, General and Administrative Expenses — Consists of expenses associated with promoting and selling our services and general and administrative functions of the business. These expenses include the costs of salaries, bonuses, fringe benefits, stock-based compensation expense, commissions, travel, legal and audit services, insurance, operating leases, advertising and other promotional activities. In addition, we pay a membership fee of 1% of revenues generated in Belarus to the administrative organization of the Belarus Hi-Tech Park. Furthermore, the Company has issued stock to the sellers and/or personnel in connection with business acquisitions and has been recognizing stock-based compensation expense in the periods after the closing of these acquisitions as part of selling, general and administrative expenses. 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 management’s 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 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, option 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. 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 acquired businesses in exchange for future services. During a performance measurement period, performance-based awards 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 a 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. Changes in the fair value of these liabilities could cause a material impact to, and volatility in the Company’s operating results. See Note 16 “Fair Value Measurements.” Employee Loans — The Company issues employee housing loans in Belarus, relocation loans to assist employees with relocation needs in connection with intra-company transfers and loans for the purchase of automobiles in India. There are no loans issued to principal officers, directors, and their affiliates. The Company intends to hold all employee loans until their maturity. Interest income is reported using the effective interest method. Where applicable, loan origination fees, net of direct origination costs, are deferred and recognized in interest income over the life of the loan. The Employee Housing Program (the “Housing Program”) provides employees with loans to purchase housing in Belarus. The housing loans are measured using the Level 3 inputs within the fair value hierarchy because they are valued using significant unobservable inputs. These housing loans are measured at fair value upon initial recognition through the market approach under ASC Topic 820, “Fair Value Measurement” and subsequently carried at amortized cost less allowance for loan losses, if any. Any difference between the carrying value and the fair value of a loan upon initial recognition is charged to expense. 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. 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 consolidated statements of cash flows. The acquired assets typically consist of customer relationships, trade names, non-competition agreements, and workforce and as a result, a substantial portion of the purchase price is allocated to goodwill and other intangible assets. Cash and Cash Equivalents — Cash equivalents are short-term, highly liquid investments that are readily convertible into cash, with maturities of three months or less at the date acquired. As of December 31, 2017 and 2016 the Company had no cash equivalents. Accounts Receivable — Accounts receivable are stated net of allowance for doubtful accounts. Outstanding accounts receivable are reviewed periodically and allowances are provided when management believes it is probable that such balances will not be collected within a reasonable time. The allowance for doubtful accounts is determined by evaluating the relative creditworthiness of each client, historical collections experience and other information, including the aging of the receivables. Accounts receivable are generally written off when they are deemed uncollectible. Bad debts are recorded based on historical experience and management’s evaluation of accounts receivable. Property and Equipment — Property and equipment acquired in the ordinary course of the Company’s operations are stated at cost, net of accumulated depreciation. Depreciation is calculated on a straight-line basis over the estimated useful lives of the assets generally ranging from two to fifty years. Leasehold improvements are amortized on a straight-line basis over the shorter of the term of the lease or the estimated useful life of the improvement. Maintenance and repairs are expensed as incurred. Long-Lived Assets — Long-lived assets, such as property and equipment and finite-lived intangible assets, are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. When the carrying value of an asset is more than the sum of the undiscounted expected future cash flows, an impairment is recognized. An impairment loss is measured as the excess of the asset’s carrying amount over its fair value. Intangible assets that have finite useful lives are amortized over their estimated useful lives on a straight-line basis. Property and equipment held for disposal are carried at the lower of the current carrying value or fair value less estimated costs to sell. The Company did not incur any impairment of long-lived assets during the years ended December 31, 2017 , 2016 and 2015 . Goodwill and Other Indefinite-Lived Intangible Assets — Goodwill and other intangible assets that have indefinite useful lives are accounted for in accordance with the FASB ASC 350, “Intangibles — Goodwill and Other.” The Company conducts its evaluation of goodwill impairment at the reporting unit level on an annual basis as of October 31st, and more frequently if events or circumstances indicate that the carrying value of a reporting unit exceeds its fair value. A reporting unit is an operating segment or one level below. The Company does not have intangible assets other than goodwill that have indefinite useful lives. Income Taxes — The provision for income taxes includes federal, state, local and foreign taxes. Deferred tax assets and liabilities are recognized for the estimated future tax consequences of temporary differences between the financial statement carrying amounts and their respective tax bases. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the year in which the temporary differences are expected to be reversed. Changes to enacted tax rates would result in either increases or decreases in the provision for income taxes in the period of changes. The realizability of deferred tax assets is primarily dependent on future earnings. The Company evaluates the realizability of deferred tax assets and recognizes a valuation allowance when it is more likely than not that all, or a portion of, deferred tax assets will not be realized. Any reduction in estimated forecasted results may require that we record valuation allowances against deferred tax assets. Once a valuation allowance has been established, it will be maintained until there is sufficient positive evidence to conclude that it is more likely than not that the deferred tax assets will be realized. A pattern of sustained profitability will generally be considered as sufficient positive evidence to reverse a valuation allowance. If the allowance is reversed in a future period, the income tax provision will be correspondingly reduced. Accordingly, the increase and decrease of valuation allowances could have a significant negative or positive impact on future earnings. See Note 10 “Income Taxes” for further information. Earnings per Share (“EPS”) — Basic EPS is computed by dividing income available to common shareholders by the weighted-average number of shares of common stock outstanding during the period. Diluted earnings per share is computed by dividing income available to common shareholders by the weighted-average number of shares of common stock outstanding during the period increased to include the number of additional shares of common stock that would have been outstanding if the potentially dilutive securities had been issued. Potentially dilutive securities include outstanding stock options, unvested restricted stock and unvested restricted stock units (“RSUs”). The dilutive effect of potentially dilutive securities is reflected in diluted earnings per share by application of the treasury stock method. Stock-Based Compensation — The Company recognizes the cost of its equity-classified stock-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. Quarterly, 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 — 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 exist that would have a material effect on the financial statements. Foreign Currency Translation — Assets and liabilities of consolidated foreign subsidiaries whose functional currency is not the U.S. dollar are translated into U.S. dollars at period-end exchange rates and revenues and expenses are translated into U.S. dollars at daily exchange rates. The adjustment resulting from translating the financial statements of such foreign subsidiaries into U.S. dollars is reflected as a cumulative translation adjustment and reported as a component of accumulated other comprehensive income (loss). For consolidated foreign subsidiaries whose functional currency is the U.S. dollar, transactions and balances denominated in the local currency are foreign currency transactions. Foreign currency transactions and balances related to non-monetary assets and liabilities are remeasured to the functional currency of the subsidiary at historical exchange rates while monetary assets and liabilities are remeasured to the functional currency of the subsidiary at current exchange rates. Foreign currency exchange gains or losses from remeasurement are included in income in the period in which they occur. Risks and Uncertainties — As a result of its global operations, the Company may be subject to certain inherent risks. Concentration of Credit — Financial instruments that potentially subject the Company to concentration of credit risk consist primarily of cash and cash equivalents, trade accounts receivable and unbilled revenues. The Company maintains cash and cash equivalents and short-term deposits with financial institutions. The Company determined that the Company’s credit policies reflect normal industry terms and business risk and there is no expectation of non-performance by the counterparties. As of December 31, 2017 , $240,148 of total cash, including time deposits and restricted cash, was held in CIS countries, with $196,656 of that total in Belarus. Banking and other financial systems in the CIS region are less developed and regulated than in some more developed markets, and bank deposits made by corporate entities in the CIS region are not insured. Changes in the market behavior or decisions of the Company’s clients could adversely affect the Company’s results of operations. During the years ended December 31, 2017 , 2016 and 2015 , revenues including reimbursable expenses and other revenues from our top five customers were $348,219 , $329,324 and $299,655 , respectively, representing 24.0% , 28.4% and 32.8% , respectively, of total revenues in the corresponding periods. Revenues including reimbursable expenses and other revenues from our top ten customers were $491,742 , $445,814 and $403,052 in 2017 , 2016 and 2015 , respectively, representing 33.9% , 38.4% and 44.1% , respectively, of total revenues in the corresponding periods. Foreign currency risk — The Company’s global operations are conducted predominantly in U.S. dollars. Other than U.S. dollars, the Company generates a significant portion of revenues in various currencies, principally, euros, British pounds sterling, Canadian dollars, Swiss francs and Russian rubles and incurs expenditures principally in Hungarian forints, Russian rubles, Polish zlotys, Swiss francs, British pounds, Indian rupees and China yuan renminbi associated with its delivery centers. The Company’s international operations expose it to foreign currency exchange rate changes that could impact translations of foreign denominated assets and liabilities into U.S. dollars and future earnings and cash flows from transactions denominated in different currencies. The Company is exposed to fluctuations in foreign currency exchange rates primarily related to accounts receivable and unbilled revenues from sales in foreign currencies and cash outflows for expenditures in foreign currencies. The Company’s results of operations, primarily revenues and expenses denominated in foreign currencies, can be affected if any of the currencies, which we use materially in our business, appreciate or depreciate against the U.S. dollar. Interest rate risk — The Company’s exposure to market risk is influenced primarily by changes in interest rates received on cash and cash equivalent deposits and paid on any outstanding balance on the Company’s revolving line of credit, which is subject to a variety of rates depending on the type and timing of funds borrowed (See Note 12 “Long-Term Debt”). The Company does not use derivative financial instruments to hedge the risk of interest rate volatility. |