EPAM Systems (EPAM) 10-K 25 Feb 21 2020 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2020	Feb. 12, 2021	Jun. 30, 2020
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2020
Document Transition Report	false
Entity File Number	001-35418
Entity Registrant Name	EPAM SYSTEMS, INC.
Entity Central Index Key	0001352010
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	22-3536104
Entity Address, Address Line One	41 University Drive
Entity Address, Address Line Two	Suite 202
Entity Address, City or Town	Newtown
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	18940
City Area Code	267
Local Phone Number	759-9000
Title of 12(b) Security	Common Stock, par value $0.001 per share
Trading Symbol	EPAM
Security Exchange Name	NYSE
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 13,559,685,089
Entity Common Stock, Shares Outstanding		56,179,461
Documents Incorporated by Reference	The registrant intends to file a definitive Proxy Statement for its 2021 annual meeting of stockholders pursuant to Regulation 14A within 120 days of the end of the registrant’s fiscal year ended December 31, 2020. Portions of the registrant’s Proxy Statement are incorporated by reference into Part III of this Annual Report on Form 10-K. With the exception of the portions of the Proxy Statement expressly incorporated by reference, such document shall not be deemed filed with this Annual Report on Form 10-K.

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Current assets
Cash and cash equivalents	$ 1,322,143	$ 936,552
Short-term investments	60,007	9
Trade receivables and contract assets, net of allowance of $4,886 and $2,920, respectively	501,062	497,716
Prepaid and other current assets	29,570	39,934
Total current assets	1,912,782	1,474,211
Property and equipment, net	169,533	165,259
Operating lease right-of-use assets, net	228,672	238,991
Intangible assets, net	51,975	56,258
Goodwill	211,956	195,043
Deferred tax assets	92,454	75,013
Other noncurrent assets	53,960	39,433
Total assets	2,721,332	2,244,208
Current liabilities
Accounts payable	10,189	7,831
Accrued compensation and benefits expenses	294,709	230,035
Accrued expenses and other current liabilities	79,690	82,476
Income taxes payable, current	20,603	9,064
Operating lease liabilities, current	60,759	57,542
Total current liabilities	465,950	386,948
Long-term debt	25,038	25,074
Income taxes payable, noncurrent	43,448	45,878
Operating lease liabilities, noncurrent	180,604	180,848
Other noncurrent liabilities	23,274	9,315
Total liabilities	738,314	648,063
Commitments and contingencies (Note 15)
Stockholders’ equity
Common stock, $0.001 par value; 160,000 authorized; 56,128 and 55,208 shares issued, 56,108 and 55,188 shares outstanding at December 31, 2020 and December 31, 2019, respectively	56	55
Additional paid-in capital	660,771	607,051
Retained earnings	1,347,880	1,020,590
Treasury stock	(177)	(177)
Accumulated other comprehensive loss	(25,512)	(31,374)
Total stockholders’ equity	1,983,018	1,596,145
Total liabilities and stockholders’ equity	$ 2,721,332	$ 2,244,208

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) shares in Thousands, $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Current assets
Trade receivables and contract assets, allowance	$ 4,886	$ 2,920
Stockholders' equity
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	160,000	160,000
Common stock, shares issued (in shares)	56,128	55,208
Common stock, shares outstanding (in shares)	56,108	55,188

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended																12 Months Ended
	Dec. 31, 2020		Sep. 30, 2020		Jun. 30, 2020		Mar. 31, 2020		Dec. 31, 2019		Sep. 30, 2019		Jun. 30, 2019		Mar. 31, 2019		Dec. 31, 2020		Dec. 31, 2019		Dec. 31, 2018
Income Statement [Abstract]
Revenues	$ 723,493		$ 652,243		$ 632,383		$ 651,359		$ 632,775		$ 588,103		$ 551,587		$ 521,333		$ 2,659,478		$ 2,293,798		$ 1,842,912
Operating expenses:
Cost of revenues (exclusive of depreciation and amortization)	465,792		423,388		419,540		423,802		410,069		377,525		355,915		344,689		1,732,522		1,488,198		1,186,921
Selling, general and administrative expenses	128,929		116,530		114,191		125,108		124,999		118,886		111,762		101,786		484,758		457,433		373,587
Depreciation and amortization expense	16,779		15,929		15,226		14,940		12,962		11,127		11,028		10,200		62,874		45,317		36,640
Income from operations	111,993		96,396		83,426		87,509		84,745		80,565		72,882		64,658		379,324		302,850		245,764
Interest and other income, net	(2,053)		1,672		1,817		2,386		1,950		2,509		1,190		3,076		3,822		8,725		3,522
Foreign exchange (loss)/gain	(7,920)		5,896		(9,167)		6,524		(1,898)		(3,105)		(3,562)		(3,484)		(4,667)		(12,049)		487
Income before provision for income taxes	102,020		103,964		76,076		96,419		84,797		79,969		70,510		64,250		378,479		299,526		249,773
Provision for income taxes	16,481		14,532		9,452		10,854		10,273		12,967		11,733		3,496		51,319		38,469		9,517
Net income	$ 85,539		$ 89,432		$ 66,624		$ 85,565		$ 74,524		$ 67,002		$ 58,777		$ 60,754		$ 327,160		$ 261,057		$ 240,256
Net income per share:
Basic (in dollars per share)	$ 1.53	[1]	$ 1.60	[1]	$ 1.20	[1]	$ 1.55	[1]	$ 1.35	[2]	$ 1.22	[2]	$ 1.07	[2]	$ 1.12	[2]	$ 5.87	[1]	$ 4.77	[2]	$ 4.48
Diluted (in dollars per share)	$ 1.46	[1]	$ 1.53	[1]	$ 1.14	[1]	$ 1.47	[1]	$ 1.29	[2]	$ 1.16	[2]	$ 1.02	[2]	$ 1.06	[2]	$ 5.60	[1]	$ 4.53	[2]	$ 4.24
Shares used in calculation of net income per share:
Basic (in shares)																	55,727		54,719		53,623
Diluted (in shares)																	58,446		57,668		56,673
[1]	Earnings per share amounts for each quarter may not necessarily total to the yearly earnings per share due to the weighting of shares outstanding on a quarterly and year to date basis.
[2]	Earnings per share amounts for each quarter may not necessarily total to the yearly earnings per share due to the weighting of shares outstanding on a quarterly and year to date basis.

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Net income	$ 327,160	$ 261,057	$ 240,256
Other comprehensive income/(loss):
Change in foreign currency translation adjustments, net of tax	4,498	6,295	(21,338)
Change in unrealized gain/(loss) on hedging instruments, net of tax	2,350	3,845	(2,553)
Defined benefit pension plans - actuarial loss, net of tax	(986)	0	0
Other comprehensive income/(loss)	5,862	10,140	(23,891)
Comprehensive income	$ 333,022	$ 271,197	$ 216,365

CONSOLIDATED STATEMENTS OF CHAN

CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Cumulative effect of adoption	Adjusted balance	Common Stock	Common StockRestricted stock	Common StockRestricted stock units	Common StockAdjusted balance	Additional Paid-in Capital	Additional Paid-in CapitalAdjusted balance	Retained Earnings	Retained EarningsCumulative effect of adoption	Retained EarningsAdjusted balance	Treasury Stock	Treasury StockAdjusted balance	Accumulated Other Comprehensive (Loss)/ Income	Accumulated Other Comprehensive (Loss)/ IncomeAdjusted balance
Balance, beginning of period at Dec. 31, 2017	$ 974,947		$ 975,404	$ 53			$ 53	$ 473,874	$ 473,874	$ 518,820		$ 519,277			$ (17,623)	$ (17,623)
Balance, beginning of period (ASU 2014-09) at Dec. 31, 2017		$ 457									$ 457
Balance, beginning of period (in shares) at Dec. 31, 2017				52,984,000			52,984,000
Treasury stock, beginning of period at Dec. 31, 2017													$ (177)	$ (177)
Treasury stock, beginning of period (in shares) at Dec. 31, 2017													20,000	20,000
Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures [Abstract]
Stock units vested (in shares)						222,000
Stock units withheld for employee taxes	(8,131)							(8,131)
Stock units withheld for employee taxes (in shares)						(71,000)
Stock Issued During Period, Value, Stock Options Exercised	34,679			$ 1				34,678
Proceeds from stock options exercises (in shares)				945,000
Stock-based compensation expense	44,279							44,279
Other comprehensive income/(loss)	(23,891)														(23,891)
Net income	240,256									240,256
Balance, end of period at Dec. 31, 2018	1,262,596			$ 54				544,700		759,533					(41,514)
Balance, end of period (in shares) at Dec. 31, 2018				54,080,000
Treasury stock, end of period at Dec. 31, 2018													$ (177)
Treasury stock, end of period (in shares) at Dec. 31, 2018													20,000
Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures [Abstract]
Stock issued in connection with acquisitions (in shares)					19,000
Stock units vested (in shares)						285,000
Stock units withheld for employee taxes	(15,951)							(15,951)
Stock units withheld for employee taxes (in shares)						(95,000)
Stock Issued During Period, Value, Stock Options Exercised	37,047			$ 1				37,046
Proceeds from stock options exercises (in shares)				899,000
Stock-based compensation expense	41,256							41,256
Other comprehensive income/(loss)	10,140														10,140
Net income	261,057									261,057
Balance, end of period at Dec. 31, 2019	$ 1,596,145		$ 1,596,275	$ 55			$ 55	607,051	$ 607,051	1,020,590		$ 1,020,720			(31,374)	$ (31,374)
Balance, end of period (ASU 2016-13) at Dec. 31, 2019		$ 130									$ 130
Balance, end of period (in shares) at Dec. 31, 2019	55,188,000			55,188,000			55,188,000
Treasury stock, end of period at Dec. 31, 2019													$ (177)	$ (177)
Treasury stock, end of period (in shares) at Dec. 31, 2019													20,000	20,000
Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures [Abstract]
Stock units vested (in shares)						327,000
Stock units withheld for employee taxes	$ (20,190)							(20,190)
Stock units withheld for employee taxes (in shares)						(106,000)
Stock Issued During Period, Value, Stock Options Exercised	26,449			$ 1				26,448
Proceeds from stock options exercises (in shares)				699,000
Stock-based compensation expense	47,462							47,462
Other comprehensive income/(loss)	5,862														5,862
Net income	327,160									327,160
Balance, end of period at Dec. 31, 2020	$ 1,983,018			$ 56				$ 660,771		$ 1,347,880					$ (25,512)
Balance, end of period (in shares) at Dec. 31, 2020	56,108,000			56,108,000
Treasury stock, end of period at Dec. 31, 2020													$ (177)
Treasury stock, end of period (in shares) at Dec. 31, 2020													20,000

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Cash flows from operating activities:
Net income	$ 327,160	$ 261,057	$ 240,256
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization expense	62,874	45,317	36,640
Operating lease right-of-use assets amortization expense	66,369	55,859	0
Bad debt expense	2,253	1,619	848
Deferred taxes	(19,994)	(7,764)	(48,000)
Stock-based compensation expense	75,238	72,036	59,188
Other	6,796	4,764	(1,712)
Changes in assets and liabilities:
Trade receivables and contract assets	4,235	(87,174)	(46,902)
Prepaid and other assets	6,983	(7,155)	(8,432)
Accounts payable	2,428	(1,685)	(772)
Accrued expenses and other liabilities	60,133	27,125	51,953
Operating lease liabilities	(64,453)	(53,419)	0
Income taxes payable	14,385	(23,127)	9,151
Net cash provided by operating activities	544,407	287,453	292,218
Cash flows from investing activities:
Purchases of property and equipment	(68,793)	(99,308)	(37,574)
Payments to Acquire Other Investments	(120,000)	0	0
Proceeds from short-term investments	60,009	0	418
Acquisition of businesses, net of cash acquired (Note 2)	(18,888)	(39,322)	(74,268)
Purchases of non-marketable securities	(20,500)	(5,000)	0
Other investing activities, net	1,018	(1,739)	(699)
Net cash used in investing activities	(167,154)	(145,369)	(112,123)
Cash flows from financing activities:
Proceeds from stock option exercises	26,410	37,003	34,845
Payments of withholding taxes related to net share settlements of restricted stock units	(20,132)	(15,503)	(7,747)
Repayment of debt (Note 9)	(18)	(9)	(3,494)
Payment of contingent consideration for previously acquired businesses	(7,004)	(1,104)	0
Other financing activities, net	(21)	(24)	(603)
Net cash (used in)/provided by financing activities	(765)	20,363	23,001
Effect of exchange rate changes on cash, cash equivalents and restricted cash	9,357	3,530	(14,240)
Net increase in cash, cash equivalents and restricted cash	385,845	165,977	188,856
Cash, cash equivalents and restricted cash, beginning of period	937,688	771,711	582,855
Cash, cash equivalents and restricted cash, end of period	1,323,533	937,688	771,711
Cash paid during the year for:
Income taxes, net of refunds	54,520	65,306	40,437
Interest	425	832	777
Supplemental disclosure of non-cash investing and financing activities
Acquisition-date fair value of contingent consideration issued for acquisition of businesses	7,119	3,876	8,390
Capital expenditures incurred but not yet paid	$ 1,582	$ 16,921	$ 2,140

CONSOLIDATED STATEMENTS OF CA_2

CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	$ 1,322,143	$ 936,552	$ 770,560
Restricted Cash and Cash Equivalents [Abstract]
Total restricted cash	1,390	1,136	1,151
Total cash, cash equivalents and restricted cash	1,323,533	937,688	771,711
Prepaid and other current assets
Restricted Cash and Cash Equivalents [Abstract]
Restricted cash current	106	0	14
Other noncurrent assets
Restricted Cash and Cash Equivalents [Abstract]
Restricted cash noncurrent	$ 1,284	$ 1,136	$ 1,137

BUSINESS AND SUMMARY OF SIGNIFI

BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES EPAM Systems, Inc. (the “Company” or “EPAM”) is a leading global provider of digital platform engineering and software development services to customers located around the world, primarily in North America, Europe, Asia and Australia. The Company’s industry expertise includes financial services, travel and consumer, software and hi-tech, business information and media, life sciences and healthcare, as well as other emerging industries. The Company is incorporated in Delaware with headquarters in Newtown, Pennsylvania. Principles of Consolidation — The consolidated financial statements include the financial statements of EPAM and its subsidiaries. All intercompany balances and transactions have been eliminated. Reclassifications — Certain amounts recorded in the prior-period consolidated balance sheets and consolidated statements of cash flows presented have been reclassified to conform to the current-period financial statement presentation. These reclassifications had no effect on previously reported results of operations . 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. Cash and Cash Equivalents — Cash equivalents are short-term, highly liquid investments and deposits that are readily convertible into cash, with maturities of three months or less at the date acquired. Highly liquid investments with maturities greater than three months at the date acquired are reported separately from cash equivalents. Trade Receivables and Contract Assets — The Company classifies its right to consideration in exchange for deliverables as either a trade receivable or a contract asset. A trade receivable is a right to consideration that is unconditional (i.e., only the passage of time is required before payment is due) regardless of whether the amounts have been billed. Trade receivables are stated net of allowance for doubtful accounts. Outstanding trade receivables are reviewed periodically and allowances are provided for the estimated amount of receivables that may not be collected. The allowance for doubtful accounts is determined based on historical experience and management’s evaluation of trade receivables. A contract asset is a right to consideration that is conditional upon factors other than the passage of time. Contract assets primarily relate to unbilled amounts on fixed-price contracts. Contract assets are recorded when services have been provided but the Company does not have an unconditional right to receive consideration. The Company recognizes an impairment loss when the contract carrying amount is greater than the remaining consideration receivable, less directly related costs to be incurred. 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. Business Combinations — The Company accounts for business combinations using the acquisition method which requires it to estimate the fair value of identifiable assets acquired and liabilities assumed, including any contingent consideration, to properly allocate the purchase price to the individual assets acquired and liabilities assumed in accordance with the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) Topic 805, Business Combinations . The allocation of the purchase price utilizes significant estimates in determining the fair values of identifiable assets acquired and liabilities assumed, especially with respect to intangible assets. The significant estimates and assumptions used include the timing and amount of forecasted revenues and cash flows, anticipated growth rates, customer attrition rates, the discount rate reflecting the risk inherent in future cash flows and the determination of useful lives for finite-lived assets. 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. The acquired assets typically include customer relationships, software, trade names, non-competition agreements, and assembled workforce and as a result, a substantial portion of the purchase price is allocated to goodwill and other intangible assets. If the 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 to present information about facts and circumstances that existed as of the acquisition date. Once the measurement period ends, which in no case extends beyond one year from the acquisition date, revisions to 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 the fair value of contingent consideration arrangements that are not measurement period adjustments are recognized in earnings. 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. Goodwill and Other Indefinite-Lived Intangible Assets — Goodwill and other intangible assets that have indefinite useful lives are accounted for in accordance with 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. Derivative Financial Instruments — The Company enters into derivative financial instruments to manage exposure to fluctuations in certain foreign currencies. During 2018, for accounting purposes, these foreign currency forward contracts became designated as hedges, as defined under FASB ASC Topic 815, Derivatives and Hedging . The Company measures these foreign currency derivative contracts at fair value on a recurring basis utilizing Level 2 inputs and recognizes them as either assets or liabilities in its consolidated balance sheets. The Company records changes in the fair value of these hedges in accumulated other comprehensive income/(loss) until the forecasted transaction occurs. When the forecasted transaction occurs, the Company reclassifies the related gain or loss on the cash flow hedge to cost of revenues (exclusive of depreciation and amortization). In the event the underlying forecasted transaction does not occur, or it becomes probable that it will not occur, the Company reclassifies the gain or loss on the underlying hedge into income. If the Company does not elect hedge accounting, or the contract does not qualify for hedge accounting treatment, the changes in fair value from period to period are recorded in income. The cash flow impact of derivatives identified as hedging instruments is reflected as cash flows from operating activities. The cash flow impact of derivatives not identified as hedging instruments is reflected as cash flows from investing activities. Fair Value of Financial Instruments — The Company makes assumptions about fair values of its financial assets and liabilities in accordance with FASB 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. Changes in the fair value of liabilities could cause a material impact to, and volatility in the Company’s operating results. See Note 4 “Fair Value Measurements.” Accumulated Other Comprehensive Loss — Accumulated other comprehensive loss (“AOCI”) consists of changes in the cumulative foreign currency translation adjustments and actuarial gains and losses on defined benefit pension plans. In addition, the Company enters into foreign currency exchange contracts, which are designated as cash flow hedges in accordance with FASB ASC Topic 815, Derivatives and Hedging. Changes in the fair values of these foreign currency exchange contracts are recognized in AOCI on the Company's consolidated balance sheets until the settlement of those contracts. Revenue Recognition — Effective January 1, 2018, the Company adopted the Accounting Standard Update (“ASU”) No. 2014-09, Revenue from Contracts with Customers (Topic 606) as amended using the modified retrospective method. The standard effectively replaced previously existing revenue recognition guidance (Topic 605) and requires entities to recognize revenue to depict the transfer of promised goods or services in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services as well as requires additional disclosure about the nature, amount, timing and uncertainty of revenues and cash flows arising from customer contracts, including significant judgments and changes in judgments. The Company applied a practical expedient to aggregate the effect of all contract modifications that occurred before the adoption date. The following table summarizes the impacts of changes in accounting policies after adoption of Topic 606 on the Company’s consolidated Statement of Income for the year ended December 31, 2018, which primarily resulted from deferring the timing of revenue recognition for contracts that were previously recognized on a cash basis and recognizing revenues from certain license agreements at a point-in-time rather than over time: Year Ended December 31, 2018 As Reported Balances Without Adoption of Topic 606 Effect of Change Higher/(Lower) Revenues $ 1,842,912 $ 1,843,159 $ (247) Income from operations $ 245,764 $ 246,011 $ (247) Provision for income taxes $ 9,517 $ 9,572 $ (55) Net income $ 240,256 $ 240,448 $ (192) The Company recognizes revenues when control of goods or services is passed to a customer in an amount that reflects the consideration the Company expects to be entitled to in exchange for those goods or services. Such control may be transferred over time or at a point in time depending on satisfaction of obligations stipulated by the contract. Consideration expected to be received may consist of both fixed and variable components and is allocated to each separately identifiable performance obligation based on the performance obligation’s relative standalone selling price. Variable consideration usually takes the form of volume-based discounts, service level credits, price concessions or incentives. Determining the estimated amount of such variable consideration involves assumptions and judgment that can have an impact on the amount of revenues reported. The Company derives revenues from a variety of service arrangements, which have been evolving to provide more customized and integrated solutions to customers by combining software engineering with customer experience design, business consulting and technology innovation services. Fees for these contracts may be in the form of time-and-materials or fixed-price arrangements. The Company generates the majority of its revenues under time-and-material contracts, which are billed using hourly, daily or monthly rates to determine the amounts to be charged directly to the customer. The Company applies a practical expedient and revenues related to time-and-material contracts are recognized based on the right to invoice for services performed. Fixed-price contracts include maintenance and support arrangements which may exceed one year in duration. Maintenance and support arrangements generally relate to the provision of ongoing services and revenues for such contracts are recognized ratably over the expected service period. Fixed-price contracts also include application development arrangements, where progress towards satisfaction of the performance obligation is measured using input or output methods and input methods are used only when there is a direct correlation between hours incurred and the end product delivered. Assumptions, risks and uncertainties inherent in the estimates used to measure progress could affect the amount of revenues, receivables and deferred revenues at each reporting period. Revenues from licenses which have significant stand-alone functionality are recognized at a point in time when control of the license is transferred to the customer. Revenues from licenses which do not have stand-alone functionality are recognized over time. If there is an uncertainty about the receipt of payment for the services, revenue recognition is deferred until the uncertainty is sufficiently resolved. The Company applies a practical expedient and does not assess the existence of a significant financing component if the period between transfer of the service to a customer and when the customer pays for that service is one year or less. The Company reports gross reimbursable “out-of-pocket” expenses incurred as both revenues and cost of revenues in the consolidated statements of income and comprehensive income. Cost of Revenues (Exclusive of Depreciation and Amortization) — Consists principally of salaries, bonuses, fringe benefits, stock-based compensation, project related travel costs and fees for subcontractors that are assigned to customer projects. Salaries and other compensation expenses of the Company’s delivery professionals are reported as cost of revenues regardless of whether the employees are actually performing customer services during a given period. Selling, General and Administrative Expenses — Consists of expenses associated with promoting and selling the Company’s services and general and administrative functions of the business. These expenses include the costs of salaries, bonuses, fringe benefits, stock-based compensation, severance, bad debt, travel, legal and accounting services, insurance, facilities including operating leases, advertising and other promotional activities. In addition, the Company pays a membership fee of 1% of revenues generated in Belarus to the administrative organization of the Belarus High-Technologies Park. Stock-Based Compensation — The Company recognizes the cost of its equity settled stock-based incentive awards based on the fair value of the award at the date of grant, net of estimated forfeitures. The cost is generally expensed evenly over the service period, unless otherwise specified by the award agreement. The service period is the period over which the employee performs the related services, which is normally the same as the vesting period. Equity-based awards that do not require future service are expensed immediately. Quarterly, the forfeiture assumption is adjusted and such adjustment may affect the timing of recognition of the total amount of expense recognized over the vesting period. Stock-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. 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. A 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. The United States subjects corporations to taxes on Global Intangible Low-Taxed Income (“GILTI”) earned by certain foreign subsidiaries. The Company elected to provide for the tax expense related to GILTI in the year the tax is incurred. 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 by 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. 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 period-end 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, cash equivalents, short-term investments and trade receivables. The Company maintains cash, cash equivalents and short-term investments with financial institutions. The Company believes its credit policies reflect normal industry terms and business risk and there is no expectation of non-performance by the counterparties. The Company has cash in banks in Belarus, Russia, Ukraine, Kazakhstan, Armenia, Georgia and Uzbekistan, where the banking sector remains subject to periodic instability. Banking and other financial systems generally do not meet the banking standards of more developed markets, and bank deposits made by corporate entities are not insured. As of December 31, 2020, $146.2 million of total cash was kept in banks in these countries, of which $52.9 million was held in Belarus. In this region, and particularly in Belarus, a banking crisis, bankruptcy or insolvency of banks that process or hold the Company’s funds, may result in the loss of deposits or adversely affect the Company’s ability to complete banking transactions in the region, which could adversely affect the Company’s business and financial condition. Cash in this region is used for the operational needs of the local entities and cash balances change with the operating needs of these entities. The Company regularly monitors cash held in these countries and, to the extent the cash held exceeds amounts required to support its operations in these countries, the Company distributes the excess funds into markets with more developed banking sectors. Trade receivables are generally dispersed across many customers operating in different industries; therefore, concentration of credit risk is limited. Historically, credit losses and write-offs of trade receivables have not been material to the consolidated financial statements. If any of our customers enter bankruptcy protection or otherwise take steps to alleviate their financial distress, including distress resulting from the COVID-19 pandemic, the Company’s credit losses and write-offs of trade receivables could increase, which would negatively impact its results of operations. Foreign currency risk — The Company’s global operations are conducted predominantly in U.S. dollars. Other than U.S. dollars, the Company generates revenues in various currencies, principally, euros, British pounds, Russian rubles, Swiss francs, and Canadian dollars and incurs expenditures principally in Russian rubles, Polish zlotys, euros, Swiss francs, Hungarian forints, British pounds, Indian rupees, Chinese yuan renminbi and Mexican pesos. 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 trade receivables 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 are used materially in the Company’s business, appreciate or depreciate against the U.S. dollar. The Company has a hedging program whereby it entered into a series of foreign exchange forward contracts with durations of twelve months or less that are designated as cash flow hedges of forecasted Russian ruble, Polish zloty and Indian rupee transactions. Interest rate risk — The Company’s exposure to market risk is influenced by the changes in interest rates received on cash and cash equivalent deposits and short-term investments and paid on any outstanding balance on the Company’s borrowings, mainly under the 2017 Credit Facility, which is subject to a variety of rates depending on the type and timing of funds borrowed (See Note 9 “Long-Term Debt”). The Company does not believe it is exposed to material direct risks associated with changes in interest rates related to these deposits and borrowings. Adoption of New Accounting Standards Unless otherwise discussed below, the adoption of new accounting standards did not have a material impact on the Company’s consolidated financial position, results of operations, and cash flows. Measurement of Credit Losses on Financial Instruments — In June 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. The amendments in this update changed how companies measure and recognize credit impairment for many financial assets. The new credit loss model requires companies to immediately recognize an estimate of credit losses expected to occur over the remaining life of the financial assets (including trade receivables) that are in the scope of the update. The update also made amendments to the current impairment model for held-to-maturity and available-for-sale debt securities and certain guarantees. The Company adopted Topic 326, effective January 1, 2020, using a modified-retrospective approach through a cumulative effect adjustment to retained earnings as of the beginning of the period of adoption. As a result of the adoption of Topic 326, the Company recorded an immaterial reduction to its allowance for doubtful accounts for trade receivables and contract assets . Leases — In February 2016, the FASB issued ASU 2016-02, Leases (“Topic 842”). The standard supersedes previously existing lease guidance (Topic 840) and requires entities to recognize all leases, with the exception of leases with a term of twelve months or less, on the balance sheet as right-of-use assets (“RoU Assets”) and lease liabilities. The guidance also changes disclosure requirements with a focus on providing information that will enable users of financial statements to assess the amount, timing and uncertainty of cash flows arising from leases. The Company adopted Topic 842, effective January 1, 2019, using the optional transition approach, which allows the Company to apply the provisions of the standard at the effective date without adjusting the comparable periods and carry forward disclosures under previously existing guidance for those periods presented within the Company’s financial statements. The Company determines if an arrangement is a lease or contains a lease at inception. The Company performs an assessment and classifies the lease as either an operating lease or a financing lease at the lease commencement date with a right-of-use asset and a lease liability recognized in the consolidated balance sheet under both classifications. The Company does not have finance leases that are material to the Company’s consolidated financial statements. Lease liabilities are initially measured at the present value of lease payments not yet paid. The present value is determined by applying the readily determinable rate implicit in the lease or, if not available, the incremental borrowing rate of the lessee. The Company determines the incremental borrowing rate of the lessee on a lease-by-lease basis by developing an estimated centralized U.S. dollar borrowing rate for a fully collateralized obligation with a term similar to the lease term and adjusts the rate to reflect the incremental risk associated with the foreign currency in which the lease is denominated. The development of this estimate includes the use of recovery rates, U.S. risk-free rates, foreign currency/country base rate yields, and a synthetic corporate credit rating of the Company developed using regression analysis. Lease agreements of the Company may include options to extend or terminate the lease and the Company includes such options in the lease term when it is reasonably certain that the Company will exercise that option. RoU Assets are recognized based on the initial measurement of the lease liabilities plus initial direct costs less lease incentives and, according to the guidance for long-lived assets, RoU Assets are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Lease expense for operating leases is recognized on a straight-line basis over the lease term. The Company elected a practical expedient to account for lease and non-lease components together as a single lease component. The Company also elected the short-term lease recognition exemption for all classes of lease assets with an original term of twelve months or less. As part of the transition, the Company elected a package of practical expedients allowing it to carry forward historical accounting for any expired or existing contracts that are or contain lease contracts, including classification of such contracts and initial direct costs associated with them. The adoption of Topic 842 on January 1, 2019 resulted in the recognition of RoU Assets for operating leases of $177.6 million and operating lease liabilities of $173.9 million. The adoption of Topic 842 did not have a material impact on the consolidated statement of income and comprehensive income, consolidated statement of changes in stockholders’ equity or the consolidated statement of cash flows. See Note 8 “Leases” in the condensed consolidated financial statements for additional information regarding leases. Pending Accounting Standards From time to time, new accounting pronouncements are issued by the FASB or other standards-setting bodies that the Company will adopt according to the various timetables the FASB specifies. The Company believes the impact of recently issued standards that are not yet effective will not have a material impact on its consolidated financial position, results of operations and cash flows upon adoption.

ACQUISITIONS

ACQUISITIONS	12 Months Ended
	Dec. 31, 2020
Business Combinations [Abstract]
ACQUISITIONS	ACQUISITIONS Continuum — On March 15, 2018, the Company acquired all of the outstanding equity of Continuum Innovation LLC together with its subsidiaries (“Continuum”) to enhance the Company’s consulting capabilities as well as its digital and service design practices. Continuum, headquartered in Boston with offices located in Milan, Seoul, and Shanghai, focuses on four practices including strategy, physical and digital design, technology and its Made Real Lab. The acquisition of Continuum added approximately 125 design consultants to the Company’s headcount. In connection with the Continuum acquisition, the Company paid $52.5 million of cash and committed to making a cash earnout payment with a maximum amount payable of $3.1 million, subject to attainment of specified performance targets in the 12 months after the acquisition date. See Note 4 “Fair Value Measurements” for more information regarding this earnout payment. Think — On November 1, 2018, the Company acquired all of the equity interests of Think Limited (“Think”), a digital transformation agency headquartered in London, UK. This acquisition is intended to strengthen EPAM’s digital and organizational consulting capabilities in the UK and Western European markets and enhance the Company’s global product and design offerings. In connection with the Think acquisition, the Company paid $26.3 million at closing and committed to making a cash earnout payment with a maximum amount payable based on exchange rates at the date of acquisition of $8.2 million subject to attainment of specified performance targets in the 12 months after the acquisition date. During the year ended December 31, 2019, the Company paid $0.2 million of net true-up payments which increased the purchase price. See Note 4 “Fair Value Measurements” for more information regarding the earnout payment. test IO — On April 30, 2019, the Company acquired 100% of the equity interests of a crowdtesting company, test IO GmbH, and its subsidiary (“test IO”). In connection with the test IO acquisition, the Company paid $17.3 million of cash. The following table summarizes the estimated fair values of the assets acquired and liabilities assumed as of the date of acquisition as updated for any changes as of December 31, 2019 for Continuum and Think and as of December 31, 2020 for test IO: Continuum Think test IO Cash and cash equivalents $ 2,251 $ 2,344 $ 663 Trade receivables and contract assets 9,139 2,637 621 Prepaid and other current assets 936 900 150 Goodwill 26,617 20,477 11,926 Intangible assets 14,450 6,882 6,219 Property and equipment and other noncurrent assets 8,902 1,214 305 Total assets acquired $ 62,295 $ 34,454 $ 19,884 Accounts payable, accrued expenses and other current liabilities $ 3,746 $ 2,025 $ 993 Long-term debt (Note 9) 3,220 — — Other noncurrent liabilities 490 — 1,568 Total liabilities assumed $ 7,456 $ 2,025 $ 2,561 Net assets acquired $ 54,839 $ 32,429 $ 17,323 During 2018, the Company adjusted initially recognized intangible assets acquired with Continuum and their useful lives, recognized an additional intangible asset in the form of a favorable lease, removed a noncurrent liability associated with an initially recognized unfavorable lease and revised the initial fair value of contingent consideration. The Company also finalized a working capital adjustment that resulted in cash collection in the amount of $0.1 million reducing the original amount of the net assets acquired. These adjustments resulted in a corresponding decrease to the originally recognized value of acquired goodwill. During the first quarter of 2019, the Company finalized the fair value of the assets acquired and liabilities assumed in the acquisition of Continuum and no additional adjustments were recorded. During 2019, the Company recorded purchase price adjustments which increased the original purchase price for Think by $0.2 million, with a corresponding adjustment to net assets acquired. In addition, the Company recorded a $1.5 million increase in deferred tax assets and other insignificant adjustments to other accounts with corresponding decreases to goodwill. During the fourth quarter of 2019, the Company finalized the fair value of the assets acquired and liabilities assumed in the acquisition of Think. During 2019, the Company recorded purchase price adjustments which increased the original purchase price for test IO and adjusted related working capital accounts increasing the original amount of the net assets acquired by $0.1 million. In addition, for the test IO acquisition, the Company reduced the value of acquired intangible assets by $0.1 million with a corresponding increase to goodwill. During the second quarter of 2020, the Company finalized the fair value of the assets acquired and liabilities assumed in the acquisition of test IO and recorded insignificant purchase price adjustments to various accounts with corresponding net decreases to goodwill of $0.2 million. The following table presents the estimated fair values and useful lives of intangible assets acquired from Continuum, Think, and test IO as of the date of acquisition and updated for any changes during the years ended December 31, 2019 for Continuum and Think and December 31, 2020 for test IO: Continuum Think test IO Weighted Average Useful Life (in years) Amount Weighted Average Useful Life (in years) Amount Weighted Average Useful Life (in years) Amount Customer relationships 6.5 $ 5,800 7 $ 6,117 7 $ 2,456 Favorable lease 11.2 5,500 — — — — Software — — — — 6 3,461 Contract royalties 8 1,900 — — — — Trade names 5 1,250 5 765 4 302 Total $ 14,450 $ 6,882 $ 6,219 In connection with the adoption of Topic 842, effective January 1, 2019, the Company reclassified the favorable lease intangible asset to Operating lease right-of-use assets. The goodwill recognized as a result of the acquisitions is attributable primarily to strategic and synergistic opportunities related to the consulting and design businesses, the assembled workforces acquired and other factors. The goodwill acquired as a result of the Continuum acquisition is expected to be deductible for income tax purposes while the goodwill acquired as a result of the Think and test IO acquisitions is not expected to be deductible for income tax purposes. Pro forma results of operations have not been presented because the effect of the acquisitions on the Company’s consolidated financial statements was not material individually or in the aggregate. Other 2019 Acquisitions — During the year ended December 31, 2019, the Company completed four additional acquisitions with an aggregate cash purchase price of $24.8 million and committed to making cash earnout payments with a maximum amount payable of $3.0 million subject to attainment of specified performance targets ranging from 12 months to 24 months after the respective acquisition dates. These acquisitions increased EPAM’s educational service and platform offerings and expanded the Company’s geographical reach, as well as added $7.5 million in intangible assets, consisting mainly of customer relationships. Pro forma results of operations have not been presented because the effect of these acquisitions on the Company’s consolidated financial statements was not material individually or in the aggregate. 2020 Acquisitions — During the year ended December 31, 2020, the Company completed two acquisitions with an aggregate purchase price of $22.5 million including contingent consideration with an aggregate acquisition-date fair value of $5.3 million. The Company committed to making contingent consideration payments with a maximum aggregate amount payable of $18.6 million subject to attainment of specified performance targets in the first and second calendar years after the respective acquisition dates. These acquisitions increased EPAM’s software and service capabilities and expanded EPAM’s offerings in financial services as well as added $7.3 million of intangible assets, consisting mainly of customer relationships. Revenues generated by these acquisitions totaled $6.0 million for the year ended December 31, 2020. Pro forma results of operations have not been presented because the effect of these acquisitions on the Company’s consolidated financial statements was not material individually or in the aggregate.

GOODWILL AND INTANGIBLE ASSETS,

GOODWILL AND INTANGIBLE ASSETS, NET	12 Months Ended
	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
GOODWILL AND INTANGIBLE ASSETS, NET	GOODWILL AND INTANGIBLE ASSETS, NET Goodwill by reportable segment was as follows: North America Europe Russia Total Balance as of January 1, 2019 $ 103,542 $ 63,290 $ — $ 166,832 test IO acquisition (Note 2) 3,301 8,849 — 12,150 Other 2019 Acquisitions (Note 2) 6,503 9,546 738 16,787 Think purchase accounting adjustments — (2,043) — (2,043) Effect of net foreign currency exchange rate changes 80 1,231 6 1,317 Balance as of December 31, 2019 113,426 80,873 744 195,043 test IO purchase accounting adjustment 863 (1,089) — (226) Other 2019 acquisitions purchase accounting adjustments 219 259 21 499 2020 Acquisitions (Note 2) 6,042 6,903 — 12,945 Effect of net foreign currency exchange rate changes 582 3,160 (47) 3,695 Balance as of December 31, 2020 $ 121,132 $ 90,106 $ 718 $ 211,956 The Russia segment had accumulated goodwill impairment losses of $2.2 million as of December 31, 2020, 2019 and 2018. There were no accumulated goodwill impairment losses in the North America or Europe reportable segments as of December 31, 2020, 2019 or 2018. Intangible assets other than goodwill as of December 31, 2020 and 2019 were as follows: As of December 31, 2020 Weighted average life at acquisition (in years) Gross carrying amount Accumulated amortization Net Customer relationships 9 $ 94,169 $ (49,415) $ 44,754 Software 6 6,309 (1,633) 4,676 Trade names 5 6,495 (5,273) 1,222 Contract royalties 8 1,900 (673) 1,227 Assembled workforce 3 157 (61) 96 Total $ 109,030 $ (57,055) $ 51,975 As of December 31, 2019 Weighted average life at acquisition (in years) Gross carrying amount Accumulated amortization Net Customer relationships 9 $ 87,489 $ (38,526) $ 48,963 Software 6 4,472 (486) 3,986 Trade names 5 6,439 (4,753) 1,686 Contract royalties 8 1,900 (435) 1,465 Assembled workforce 3 158 — 158 Total $ 100,458 $ (44,200) $ 56,258 All of the intangible assets other than goodwill have finite lives and as such are subject to amortization. Amortization of the other intangible assets is recognized in depreciation and amortization expense in the consolidated statements of income and comprehensive income. The following table presents amortization expense recognized for the periods indicated: For the Years Ended December 31, 2020 2019 2018 Customer relationships $ 10,478 $ 8,743 $ 7,637 Software 1,068 486 — Trade names 495 447 266 Contract royalties 238 238 198 Assembled workforce 61 — — Favorable lease — — 410 Total $ 12,340 $ 9,914 $ 8,511 In connection with the adoption of Topic 842, effective January 1, 2019, the Company reclassified the favorable lease intangible asset to Operating lease right-of-use assets. See Note 8 “Leases” for further information regarding the Company’s operating leases. Based on the carrying value of the Company’s existing intangible assets as of December 31, 2020, the estimated amortization expense for the future years is as follows: Year ending December 31, Amount 2021 $ 12,585 2022 12,426 2023 11,115 2024 8,586 2025 5,543 Thereafter 1,720 Total $ 51,975

FAIR VALUE MEASUREMENTS

FAIR VALUE MEASUREMENTS	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
FAIR VALUE MEASUREMENTS	FAIR VALUE MEASUREMENTS The Company carries certain assets and liabilities at fair value on a recurring basis on its consolidated balance sheets. The following table shows the fair values of the Company’s financial assets and liabilities measured at fair value on a recurring basis as of December 31, 2020: As of December 31, 2020 Balance Level 1 Level 2 Level 3 Foreign exchange derivative assets $ 4,955 $ — $ 4,955 $ — Total assets measured at fair value on a recurring basis $ 4,955 $ — $ 4,955 $ — Foreign exchange derivative liabilities $ 243 $ — $ 243 $ — Contingent consideration 7,470 — — 7,470 Total liabilities measured at fair value on a recurring basis $ 7,713 $ — $ 243 $ 7,470 The following table shows the fair values of the Company’s financial assets and liabilities measured at fair value on a recurring basis as of December 31, 2019. As of December 31, 2019 Balance Level 1 Level 2 Level 3 Foreign exchange derivative assets $ 1,910 $ — $ 1,910 $ — Total assets measured at fair value on a recurring basis $ 1,910 $ — $ 1,910 $ — Foreign exchange derivative liabilities $ 243 $ — $ 243 $ — Contingent consideration 10,495 — — 10,495 Total liabilities measured at fair value on a recurring basis $ 10,738 $ — $ 243 $ 10,495 The foreign exchange derivatives are valued using pricing models and discounted cash flow methodologies based on observable foreign exchange data at the measurement date. See Note 5 “Derivative Financial Instruments” for additional information regarding derivative financial instruments. The fair value of the contingent consideration was determined using a probability-weighted expected return method and is based on the expected future payments to be made to the sellers of the acquired businesses in accordance with the provisions outlined in the respective purchase agreements. Although there is significant judgment involved, the Company believes its estimates and assumptions are reasonable. In determining fair value, the Company considered a variety of factors, including future performance of the acquired businesses using financial projections developed by the Company and market risk assumptions that were derived for revenue growth and earnings before interest and taxes. The Company estimated future payments using the earnout formula and performance targets specified in the purchase agreements and adjusted those estimates to reflect the probability of their achievement. Those weighted-average estimated future payments were then discounted to present value using a rate based on the weighted-average cost of capital of guideline companies. The discount rates used to determine the fair value of contingent consideration for the 2020 Acquisitions ranged from a minimum of 15.5% to a maximum of 17.5%. Changes in financial projections, market risk assumptions, discount rates or probability assumptions related to achieving the various earnout criteria would result in a change in the fair value of the recorded contingent liabilities. Such changes, if any, are recorded within Interest and other income, net in the Company’s consolidated statement of income and comprehensive income. In connection with the Continuum acquisition, the Company committed to making a cash earnout payment subject to attainment of specified performance targets in the 12 months after the acquisition date. As of the acquisition date, the Company recorded a $2.4 million contingent consideration liability related to this earnout payment and, subsequently, reduced this liability by $0.9 million during 2018 and $0.4 million during 2019 due to the change in its fair value. The Company extinguished the earnout obligation during 2019 by paying $1.1 million in cash. In connection with the Think acquisition, the Company committed to making a cash earnout payment subject to attainment of specified performance targets in the 12 months after the acquisition date. As of the acquisition date, the Company recorded a $6.0 million liability related to this earnout payment as contingent consideration and, subsequently, increased this liability by $2.2 million during 2019 due to the change in its fair value. The Company extinguished the earnout obligation during 2020 by paying $7.9 million in cash. In connection with the Company’s Other 2019 Acquisitions, the Company committed to making cash earnout payments subject to attainment of specified performance targets ranging from 12 months to 24 months after the respective acquisition dates. During 2020, the Company extinguished part of this earnout obligation by paying $1.8 million in cash. See Note 2 “Acquisitions” in the consolidated financial statements for additional information regarding business acquisitions. A reconciliation of the beginning and ending balances of Level 3 acquisition-related contractual contingent consideration using significant unobservable inputs for the years ended December 31, 2018, December 31, 2019 and December 31, 2020 are as follows: Amount Contractual contingent liabilities as of January 1, 2018 $ — Acquisition date fair value of contingent consideration — Continuum acquisition (Note 2) 2,400 Acquisition date fair value of contingent consideration — Think acquisition (Note 2) 5,990 Changes in fair value of contingent consideration included in Interest and other income, net (900) Effect of net foreign currency exchange rate changes (22) Contractual contingent liabilities as of December 31, 2018 $ 7,468 Payment of contingent consideration for previously acquired businesses (1,104) Acquisition date fair value of contingent consideration — Other 2019 Acquisitions (Note 2) 2,100 Changes in fair value of contingent consideration included in Interest and other income, net 1,776 Effect of net foreign currency exchange rate changes 255 Contractual contingent liabilities as of December 31, 2019 $ 10,495 Payment of contingent consideration for previously acquired businesses (9,619) Acquisition date fair value of contingent consideration — 2020 Acquisitions (Note 2) 5,292 Changes in fair value of contingent consideration included in Interest and other income, net 1,827 Effect of net foreign currency exchange rate changes (525) Contractual contingent consideration liabilities as of December 31, 2020 $ 7,470 Financial Assets and Liabilities Not Measured at Fair Value on a Recurring Basis Estimates of fair value of financial instruments not carried at fair value on a recurring basis on the Company’s consolidated balance sheets are generally subjective in nature, and are determined as of a specific point in time based on the characteristics of the financial instruments and relevant market information. The Company uses the following methods to estimate the fair values of its financial instruments: • for financial instruments that have quoted market prices, those quoted prices are used to estimate fair value; • for financial instruments for which no quoted market prices are available, fair value is estimated using information obtained from independent third parties, or by discounting the expected cash flows using an estimated current market interest rate for the financial instrument; • for financial instruments for which no quoted market prices are available and that have no defined maturity, have a remaining maturity of 360 days or less, or reprice frequently to a market rate, the Company assumes that the fair value of these instruments approximates their reported value, after taking into consideration any applicable credit risk. The generally short maturities of certain assets and liabilities result in a number of assets and liabilities for which fair value equals or closely approximates the amount recorded on the Company’s consolidated balance sheets. Such financial assets and liabilities that are not carried at fair value on a recurring basis on the Company’s consolidated balance sheets are cash equivalents, restricted cash, short-term investments, employee loans and long-term debt (Note 9 “Long-Term Debt”). The following tables present the estimated fair values of the Company’s financial assets and liabilities not measured at fair value on a recurring basis as of the dates indicated: Fair Value Hierarchy Balance Estimated Fair Value Level 1 Level 2 Level 3 December 31, 2020 Financial Assets: Cash equivalents: Money market funds $ 153,783 $ 153,783 $ 153,783 $ — $ — Total cash equivalents $ 153,783 $ 153,783 $ 153,783 $ — $ — Restricted cash $ 1,390 $ 1,390 $ 1,390 $ — $ — Time deposits included in Short-term investments $ 60,007 $ 60,007 $ — $ 60,007 $ — Employee loans $ 794 $ 794 $ — $ — $ 794 Financial Liabilities: Borrowings under 2017 Credit Facility $ 25,007 $ 25,007 $ — $ 25,007 $ — Fair Value Hierarchy Balance Estimated Fair Value Level 1 Level 2 Level 3 December 31, 2019 Financial Assets: Cash equivalents: Money market funds $ 407,817 $ 407,817 $ 407,817 $ — $ — Time deposits 10,002 10,002 — 10,002 — Total cash equivalents $ 417,819 $ 417,819 $ 407,817 $ 10,002 $ — Restricted cash $ 1,136 $ 1,136 $ 1,136 $ — $ — Employee loans $ 2,434 $ 2,434 $ — $ — $ 2,434 Financial Liabilities: Borrowings under 2017 Credit Facility $ 25,017 $ 25,017 $ — $ 25,017 $ — Non-Marketable Securities Without Readily Determinable Fair Values The Company holds investments in equity securities that do not have readily determinable fair values. These investments are recorded at cost and are remeasured to fair value based on certain observable price changes or impairment events as they occur. The carrying amount of these investments was $25.0 million and $5.8 million as of December 31, 2020 and December 31, 2019, respectively and is classified as Other noncurrent assets in the Company’s consolidated balance sheets.

DERIVATIVE FINANCIAL INSTRUMENT

DERIVATIVE FINANCIAL INSTRUMENTS	12 Months Ended
	Dec. 31, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]
DERIVATIVE FINANCIAL ISTRUMENTS	DERIVATIVE FINANCIAL INSTRUMENTS In the normal course of business, the Company uses derivative financial instruments to manage the risk of fluctuations in foreign currency exchange rates. The Company has a hedging program whereby it enters into a series of foreign exchange forward contracts with durations of twelve months or less that are designated as cash flow hedges of forecasted Russian ruble, Polish zloty and Indian rupee transactions. The Company measures derivative instruments and hedging activities at fair value and recognizes them as either assets or liabilities in its consolidated balance sheets. Accounting for the gains and losses resulting from changes in fair value depends on the use of the derivative and whether it is designated and qualifies for hedge accounting. To receive hedge accounting treatment, all hedging relationships are formally documented at the inception of the hedge, and the hedges must be highly effective in offsetting changes to future cash flows on hedged transactions. As of December 31, 2020, all of the Company’s foreign exchange forward contracts were designated as hedges. Derivatives may give rise to credit risks from the possible non-performance by counterparties. The Company has limited its credit risk by entering into derivative transactions only with highly-rated financial institutions and by conducting an ongoing evaluation of the creditworthiness of the financial institutions with which the Company does business. There is no financial collateral (including cash collateral) required to be posted by the Company related to the foreign exchange forward contracts. The fair value of foreign currency derivative instruments on the Company’s consolidated balance sheets as of December 31, 2020 and December 31, 2019 were as follows: As of December 31, 2020 As of December 31, 2019 Balance Sheet Classification Asset Derivatives Liability Derivatives Asset Derivatives Liability Derivatives Foreign exchange forward contracts - Designated as hedging instruments Prepaid and other current assets $ 4,955 $ 1,910 Accrued expenses and other current liabilities $ 243 $ 243

PROPERTY AND EQUIPMENT, NET

PROPERTY AND EQUIPMENT, NET	12 Months Ended
	Dec. 31, 2020
Property, Plant and Equipment [Abstract]
PROPERTY AND EQUIPMENT, NET	PROPERTY AND EQUIPMENT, NET Property and equipment, net consisted of the following: Weighted Average Useful Life As of December 31, 2020 As of December 31, 2019 Computer hardware 3 $ 117,333 $ 96,286 Buildings 46 52,007 51,300 Leasehold improvements 7 39,675 30,634 Purchased computer software 3 31,993 32,115 Furniture, fixture and other equipment 7 31,859 28,193 Office equipment 7 20,971 18,901 Land improvements 18 2,137 2,137 Land n/a 1,339 — 297,314 259,566 Less accumulated depreciation and amortization (127,781) (94,307) Total $ 169,533 $ 165,259 Depreciation and amortization expense related to property and equipment was $50.5 million, $35.4 million and $28.5 million during the years ended December 31, 2020, 2019 and 2018, respectively. On November 1, 2019, the Company acquired an office building in Minsk, Belarus for $18.9 million, excluding refundable VAT. The acquired building is intended to be used in the Company’s normal operations as office space for its employees; however, a portion of the building was leased to third parties under operating lease agreements prior to the Company’s purchase and the Company will continue leasing under those agreements (see Note 8 “Leases”). In addition to this building, the Company has other assets which generate lease income. The gross amount of such assets including the leased portion of the Minsk building was $6.7 million and $10.7 million, and the associated accumulated depreciation was $0.2 million and $0.1 million as of December 31, 2020 and 2019, respectively. Depreciation expense associated with these assets held under operating leases was $0.2 million and $0.1 million for the year ended December 31, 2020 and 2019, respectively.

ACCRUED EXPENSES AND OTHER CURR

ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES	12 Months Ended
	Dec. 31, 2020
Payables and Accruals [Abstract]
ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES	ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES Accrued expenses and other current liabilities consisted of the following: As of December 31, 2020 As of December 31, 2019 Value added taxes payable $ 34,522 $ 24,016 Deferred revenue 17,383 9,132 Contingent consideration, current (Note 4) 1,125 10,057 Other current liabilities and accrued expenses 26,660 39,271 Total $ 79,690 $ 82,476

LEASES

LEASES	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
LEASES	LEASES The Company leases office space, corporate apartments, office equipment, and vehicles. Many of the Company’s leases contain variable payments including changes in base rent and charges for common area maintenance or other miscellaneous expenses. Due to this variability, the cash flows associated with these variable payments are not included in the minimum lease payments used in determining the RoU Assets and associated lease liabilities and are recognized in the period in which the obligation for such payments is incurred. The Company’s leases have remaining lease terms ranging from 0.1 to 10.4 years. Certain lease agreements, mainly for office space, include options to extend or terminate the lease before the expiration date. The Company considers such options when determining the lease term when it is reasonably certain that the Company will exercise that option. The Company leases and subleases a portion of its office space to third parties. Lease income and sublease income were immaterial for the years ended December 31, 2020, 2019 and 2018. During the years ended December 31, 2020 and 2019, the components of lease expense were as follows: Income Statement Classification Year Ended December 31, 2020 Year Ended December 31, 2019 Operating lease cost Selling, general and administrative expenses $ 73,740 $ 62,740 Variable lease cost Selling, general and administrative expenses 6,461 8,730 Short-term lease cost Selling, general and administrative expenses 1,169 3,870 Total lease cost $ 81,370 $ 75,340 Lease expense under operating lease agreements for the year ended December 31, 2018 was $46.9 million. Supplemental cash flow information related to leases was as follows: Year Ended December 31, 2020 Year Ended December 31, 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows used for operating leases $ 70,012 $ 59,952 Right-of-use assets obtained in exchange for lease obligations: Operating leases $ 50,949 $ 107,822 Non-cash net increase due to lease modifications: Operating lease right-of-use assets $ 7,876 $ 10,124 Operating lease liabilities $ 7,861 $ 10,192 Weighted average remaining lease terms and discount rates as of December 31, 2020, were as follows: As of December 31, 2020 As of December 31, 2019 Weighted average remaining lease term, in years: Operating leases 5.9 6.1 Weighted average discount rate: Operating leases 2.9 % 3.6 % As of December 31, 2020, operating lease liabilities will mature as follows: Year ending December 31, Lease Payments 2021 $ 66,585 2022 50,147 2023 37,268 2024 32,400 2025 22,859 Thereafter 52,531 Total lease payments 261,790 Less: imputed interest (20,427) Total $ 241,363 There were no lease agreements that contained material restrictive covenants or material residual value guarantees as of December 31, 2020. There were no material lease agreements signed with related parties as of December 31, 2020. As of December 31, 2020, the Company had committed to payments of $1.0 million related to operating lease agreements that had not yet commenced as of December 31, 2020. These operating leases will commence on various dates during 2021 with lease terms ranging from 1 year to 5 years. The Company does not have any material finance lease agreements that had not yet commenced.

LONG-TERM DEBT

LONG-TERM DEBT	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
LONG-TERM DEBT	LONG-TERM DEBT Revolving Line of Credit —On May 24, 2017, the Company entered into an unsecured credit facility (the “2017 Credit Facility”), as may be amended from time to time, with PNC Bank, National Association; PNC Capital Markets LLC; Citibank N.A.; Wells Fargo Bank, National Association; Fifth Third Bank and Santander Bank, N.A. (collectively the “Lenders”). The 2017 Credit Facility provides for a borrowing capacity of $300.0 million, with potential to increase the credit facility up to $400.0 million if certain conditions are met. The 2017 Credit Facility matures on May 24, 2022. Borrowings under the 2017 Credit Facility may be denominated in U.S. dollars or up to a maximum of $100.0 million in British pounds, Canadian dollars, euros and Swiss francs and other currencies as may be approved by the administrative agent and the Lenders. Borrowings under the 2017 Credit Facility bear interest at either a base rate or Euro-rate plus a margin based on the Company’s leverage ratio. The base rate is equal to the highest of (a) the Overnight Bank Funding Rate, plus 0.5%, (b) the Prime Rate, or (c) the Daily LIBOR Rate, plus 1.0%. As of December 31, 2020, the Company’s outstanding borrowings are subject to a LIBOR-based interest rate, which resets regularly at issuance, based on lending terms. The 2017 Credit Facility includes customary business and financial covenants that may restrict the Company’s ability to make or pay dividends (other than certain intercompany dividends) if a potential or an actual event of default has occurred or would be triggered. As of December 31, 2020, the Company was in compliance with all covenants contained in the 2017 Credit Facility. The following table presents the outstanding debt and borrowing capacity of the Company under the 2017 Credit Facility: As of December 31, 2020 As of December 31, 2019 Outstanding debt $ 25,000 $ 25,000 Interest rate 1.2 % 2.8 % Irrevocable standby letters of credit $ — $ 303 Available borrowing capacity $ 275,000 $ 274,697 Current maximum borrowing capacity $ 300,000 $ 300,000 As part of the acquisition of Continuum in 2018, the Company assumed $3.4 million of long-term debt associated with a leased facility and payable to Continuum’s landlord. The debt was payable in monthly installments through March 31, 2029 and bore interest at a rate of 8% per annum. In March 2018, the Company paid $3.4 million to settle this assumed long-term debt.

PENSION AND POSTRETIREMENT BENE

PENSION AND POSTRETIREMENT BENEFITS	12 Months Ended
	Dec. 31, 2020
Retirement Benefits [Abstract]
PENSION AND POSTRETIREMENT BENEFITS	PENSION AND POSTRETIREMENT BENEFITS Defined Contribution Pension Plans The Company offers defined contribution plans for its employees in certain countries including a 401(k) retirement plan covering substantially all of the Company’s U.S. employees. Employer contributions charged to expense for defined contribution benefit plans for the years ended December 31, 2020, 2019 and 2018, were $16.0 million, $14.8 million, and $6.5 million, respectively. Defined Benefit Pension Plans The Company sponsors defined benefit pension plans for its employees in certain countries as governed by local regulatory requirements. During the years ended December 31, 2020, 2019 and 2018, the Company recorded expense of $4.3 million, $1.4 million and $2.6 million, respectively, related to these plans. During the year ended December 31, 2020, we recorded net actuarial loss as a component of net periodic benefit cost of $1.3 million as accumulated other comprehensive loss. The net unfunded balance of our defined benefit pension plans was $6.4 million as of December 31, 2020 of which $1.0 million is included in Accrued compensation and benefits expense and $5.4 million is classified in Other noncurrent liabilities in our consolidated balance sheet. The net unfunded balance of our defined benefit pension plans was $3.9 million as of December 31, 2019 of which $0.3 million is included in Accrued compensation and benefits expense and $3.6 million is classified in Other noncurrent liabilities in our consolidated balance sheet.

REVENUES

REVENUES	12 Months Ended
	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
REVENUES	REVENUESRevenues are sourced from four geographic markets: North America, Europe, CIS and APAC. The Company presents and discusses revenues by customer location based on the location of the specific customer site that we serve, irrespective of the location of the headquarters of the customer or the location of the delivery center where the work is performed. Revenues by customer location is different from revenues by reportable segment as segments are not based on the geographic location of the customers, but instead they are based on the location of the Company’s management responsible for a particular customer or market (see Note 16 “Segment Information”). The Company assigns customers into one of five vertical industries or a group of various industries where the Company is increasing its presence, which are labeled as “Emerging Verticals”. Emerging Verticals include customers in multiple industries such as energy, utilities, manufacturing, automotive, telecommunications and several others. Disaggregation of Revenues The following tables show the disaggregation of the Company’s revenues by major customer location, including a reconciliation of the disaggregated revenues with the Company’s reportable segments (Note 16 “Segment Information”) for the years ended December 31, 2020, 2019 and 2018: Year Ended December 31, 2020 Reportable Segments North America Europe Russia Consolidated Revenues Customer Locations North America $ 1,546,093 $ 45,553 $ 3,490 $ 1,595,136 Europe 45,733 834,033 76 879,842 CIS 7,817 98 106,787 114,702 APAC 2,177 67,621 — 69,798 Revenues $ 1,601,820 $ 947,305 $ 110,353 $ 2,659,478 Year Ended December 31, 2019 Reportable Segments North America Europe Russia Consolidated Revenues Customer Locations North America $ 1,344,040 $ 45,859 $ 116 $ 1,390,015 Europe 27,042 719,548 276 746,866 CIS 8,583 143 91,745 100,471 APAC 1,279 55,167 — 56,446 Revenues $ 1,380,944 $ 820,717 $ 92,137 $ 2,293,798 Year Ended December 31, 2018 Reportable Segments North America Europe Russia Consolidated Revenues Customer Locations North America $ 1,046,232 $ 52,860 $ 75 $ 1,099,167 Europe 16,679 595,741 52 612,472 CIS 8,437 336 72,930 81,703 APAC 5,631 43,848 91 49,570 Revenues $ 1,076,979 $ 692,785 $ 73,148 $ 1,842,912 The following tables show the disaggregation of the Company’s revenues by industry vertical, including a reconciliation of the disaggregated revenues with the Company’s reportable segments (Note 16 “Segment Information”) for the years ended December 31, 2020, 2019 and 2018: Year Ended December 31, 2020 Reportable Segments North America Europe Russia Consolidated Revenues Industry Verticals Business Information & Media $ 334,063 $ 224,922 $ 1,695 $ 560,680 Financial Services 199,594 278,355 77,286 555,235 Software & Hi-Tech 419,895 73,288 3,630 496,813 Travel & Consumer 221,977 220,448 16,364 458,789 Life Sciences & Healthcare 260,518 35,347 448 296,313 Emerging Verticals 165,773 114,945 10,930 291,648 Revenues $ 1,601,820 $ 947,305 $ 110,353 $ 2,659,478 Year Ended December 31, 2019 Reportable Segments North America Europe Russia Consolidated Revenues Industry Verticals Business Information & Media $ 262,448 $ 157,844 $ 631 $ 420,923 Financial Services 184,469 244,284 72,119 500,872 Software & Hi-Tech 354,023 77,377 1,998 433,398 Travel & Consumer 198,264 229,523 11,571 439,358 Life Sciences & Healthcare 224,925 23,444 83 248,452 Emerging Verticals 156,815 88,245 5,735 250,795 Revenues $ 1,380,944 $ 820,717 $ 92,137 $ 2,293,798 Year Ended December 31, 2018 Reportable Segments North America Europe Russia Consolidated Revenues Industry Verticals Business Information & Media $ 251,081 $ 72,898 $ 54 $ 324,033 Financial Services $ 112,444 $ 252,196 $ 59,337 $ 423,977 Software & Hi-Tech 269,067 79,121 2,627 350,815 Travel & Consumer 177,910 208,266 7,467 393,643 Life Sciences & Healthcare 151,418 20,272 13 171,703 Emerging Verticals 115,059 60,032 3,650 178,741 Revenues $ 1,076,979 $ 692,785 $ 73,148 $ 1,842,912 The Company derives revenues from a variety of customized and integrated service arrangements. Fees for these contracts may be in the form of time-and-materials or fixed-price arrangements. The following tables show the disaggregation of the Company’s revenues by contract type, including a reconciliation of the disaggregated revenues with the Company’s reportable segments (Note 16 “Segment Information”) for the years ended December 31, 2020, 2019 and 2018: Year Ended December 31, 2020 Reportable Segments North America Europe Russia Consolidated Revenues Contract Types Time-and-material $ 1,440,635 $ 790,203 $ 60,166 $ 2,291,004 Fixed-price 151,769 151,718 48,525 352,012 Licensing 8,027 1,526 1,586 11,139 Other revenues 1,389 3,858 76 5,323 Revenues $ 1,601,820 $ 947,305 $ 110,353 $ 2,659,478 Year Ended December 31, 2019 Reportable Segments North America Europe Russia Consolidated Revenues Contract Types Time-and-material $ 1,247,979 $ 688,605 $ 54,069 $ 1,990,653 Fixed-price 127,926 128,977 37,747 294,650 Licensing 3,626 1,230 225 5,081 Other revenues 1,413 1,905 96 3,414 Revenues $ 1,380,944 $ 820,717 $ 92,137 $ 2,293,798 Year Ended December 31, 2018 Reportable Segments North America Europe Russia Consolidated Revenues Contract Types Time-and-material $ 983,436 $ 628,707 $ 40,754 $ 1,652,897 Fixed-price 89,831 62,078 32,342 184,251 Licensing 2,748 1,332 17 4,097 Other revenues 964 668 35 1,667 Revenues $ 1,076,979 $ 692,785 $ 73,148 $ 1,842,912 Timing of Revenue Recognition The following tables show the timing of revenue recognition: Year Ended December 31, 2020 Reportable Segments North America Europe Russia Consolidated Revenues Timing of Revenue Recognition Transferred over time $ 1,595,786 $ 946,379 $ 108,826 $ 2,650,991 Transferred at a point of time 6,034 926 1,527 8,487 Revenues $ 1,601,820 $ 947,305 $ 110,353 $ 2,659,478 Year Ended December 31, 2019 Reportable Segments North America Europe Russia Consolidated Revenues Timing of Revenue Recognition Transferred over time $ 1,379,256 $ 819,913 $ 92,076 $ 2,291,245 Transferred at a point of time 1,688 804 61 2,553 Revenues $ 1,380,944 $ 820,717 $ 92,137 $ 2,293,798 Year Ended December 31, 2018 Reportable Segments North America Europe Russia Consolidated Revenues Timing of Revenue Recognition Transferred over time $ 1,076,084 $ 692,023 $ 73,135 $ 1,841,242 Transferred at a point of time 895 762 13 1,670 Revenues $ 1,076,979 $ 692,785 $ 73,148 $ 1,842,912 During the years ended December 31, 2020, 2019 and 2018 the Company recognized $5.0 million, $7.8 million and $5.7 million, respectively, of revenues from performance obligations satisfied in previous periods. The following table includes the estimated revenues expected to be recognized in the future related to performance obligations that are partially or fully unsatisfied as of December 31, 2020. The Company applies a practical expedient and does not disclose the value of unsatisfied performance obligations for contracts that (i) have an original expected duration of one year or less and (ii) contracts for which it recognizes revenues at the amount to which it has the right to invoice for services provided: Less than 1 year 1 Year 2 Years 3 Years Total Contract Type Fixed-price $ 7,885 $ 103 $ — $ — $ 7,988 The Company applies a practical expedient and does not disclose the amount of the transaction price allocated to the remaining performance obligations nor provide an explanation of when the Company expects to recognize that amount as revenue for certain variable consideration. Contract Balances The following table provides information on the classification of contract assets and liabilities in the consolidated balance sheets: As of December 31, 2020 As of December 31, 2019 Contract assets included in Trade receivables and contract assets $ 7,700 $ 14,320 Contract liabilities included in Accrued expenses and other current liabilities $ 17,383 $ 9,132 Contract liabilities included in Other noncurrent liabilities $ 94 $ 5 Contract assets have decreased from December 31, 2019 primarily due to reduced receivables from projects where our right to bill is contingent on something other than passage of time partially attributable to the change of a specific project to time-and-material billing in 2020. Contract liabilities comprise amounts collected from the Company’s customers for revenues not yet earned. Such amounts are anticipated to be recorded as revenues when services are performed in subsequent periods. Contract liabilities have increased from December 31, 2019 due to an increase in customer advances largely attributable to contracts with multiple performance obligations. During the year ended December 31, 2020, the Company recognized $8.6 million of revenues that were included in Accrued expenses and other current liabilities at December 31, 2019. During the year ended December 31, 2019, the Company recognized $3.9 million of revenues that were included in Accrued expenses and other current liabilities at December 31, 2018.

STOCK-BASED COMPENSATION

STOCK-BASED COMPENSATION	12 Months Ended
	Dec. 31, 2020
Share-based Payment Arrangement [Abstract]
STOCK-BASED COMPENSATION	STOCK-BASED COMPENSATION The following costs related to the Company’s stock compensation plans were included in the consolidated statements of income and comprehensive income: For the Years Ended December 31, 2020 2019 2018 Cost of revenues (exclusive of depreciation and amortization) $ 32,785 $ 37,580 $ 27,245 Selling, general and administrative expenses 42,453 34,456 31,943 Total $ 75,238 $ 72,036 $ 59,188 Equity Plans 2015 Long-Term Incentive Plan — On June 11, 2015, the Company’s stockholders approved the 2015 Long-Term Incentive Plan (“2015 Plan”) to be used to issue equity awards to company personnel. As of December 31, 2020, 4,549 thousand shares of common stock remained available for issuance under the 2015 Plan. All of the awards issued pursuant to the 2015 Plan expire 10 years from the date of grant. 2012 Non-Employee Directors Compensation Plan — On January 11, 2012, the Company approved the 2012 Non-Employee Directors Compensation Plan (“2012 Directors Plan”) to be used to issue equity grants to its non-employee directors. The Company authorized 600 thousand shares of common stock to be reserved for issuance under the plan. As of December 31, 2020, 524 thousand shares of common stock remained available for issuance under the 2012 Directors Plan. The 2012 Directors Plan will expire after 10 years and is administered by the Company’s Board of Directors. 2012 Long-Term Incentive Plan — On January 11, 2012, the Company approved the 2012 Long-Term Incentive Plan (“2012 Plan”) to be used to issue equity grants to Company personnel. In June 2015, the 2012 Plan was discontinued; however, outstanding awards remain subject to the terms of the 2012 Plan and any shares that are subject to an award that was previously granted under the 2012 Plan and that expire or terminate for any reason prior to exercise will become available for issuance under the 2015 Plan. All of the awards issued pursuant to the 2012 Plan expire 10 years from the date of grant. 2006 Stock Option Plan — Effective May 31, 2006, the Board of Directors of the Company adopted the 2006 Stock Option Plan (the “2006 Plan”) to grant stock options to directors, employees, and certain independent contractors. In January 2012, the 2006 Plan was discontinued; however, outstanding awards remain subject to the terms of the 2006 Plan and any shares that are subject to an option award that was previously granted under the 2006 Plan and that expire or terminate for any reason prior to exercise will become available for issuance under the 2015 Plan. All of the awards issued pursuant to the 2006 Plan expire 10 years from the date of grant. Stock Options Stock option activity under the Company’s plans is set forth below: Number of Weighted Average Aggregate Weighted Average Options outstanding as of January 1, 2018 4,902 $ 40.91 $ 326,064 Options granted 160 $ 112.81 Options exercised (945) $ 36.69 Options forfeited/cancelled (33) $ 63.28 Options expired (1) $ 25.72 Options outstanding as of December 31, 2018 4,083 $ 44.54 $ 291,846 Options granted 132 $ 169.13 Options modified 18 $ 163.55 Options exercised (899) $ 41.21 Options forfeited/cancelled (11) $ 97.83 Options outstanding as of December 31, 2019 3,323 $ 50.85 $ 536,015 Options granted 158 $ 187.76 Options modified — $ — Options exercised (700) $ 37.79 Options forfeited/cancelled (9) $ 119.30 Options outstanding as of December 31, 2020 2,772 $ 61.71 $ 822,152 4.3 Options vested and exercisable as of December 31, 2020 2,388 $ 46.99 $ 743,582 3.7 Options expected to vest as of December 31, 2020 362 $ 152.22 $ 74,548 8.2 The fair value of each option award is estimated on the date of grant using the Black-Scholes option valuation model. The model incorporated the following weighted-average assumptions: For the Years Ended December 31, 2020 2019 2018 Expected volatility 36.9 % 33.5 % 33.8 % Expected term (in years) 6.25 6.25 6.25 Risk-free interest rate 0.5 % 2.3 % 2.7 % Expected dividends — % — % — % Expected volatility is based on historical volatility of the Company’s stock price. The expected life represents the period of time that options granted are expected to be outstanding. The risk-free rate is based on the U.S. Treasury yield curve for periods equal to the expected term of the options in effect at the time of grant. The Company has not declared or paid any dividends on its common stock. The Company intends to retain any earnings to fund operations and future growth of its business and, therefore, does not anticipate paying any cash dividends in the foreseeable future. The weighted-average grant-date fair value of stock options granted during the years ended December 31, 2020, 2019 and 2018 was $68.53, $63.12 and $43.42, respectively. The total intrinsic value of options exercised during the years ended December 31, 2020, 2019 and 2018 was $151.3 million, $121.1 million and $83.3 million, respectively. The Company recognizes the fair value of each option as compensation expense on a straight-line basis over the requisite service period, which is generally the vesting period. The options are typically scheduled to vest over four years from the time of grant, subject to the terms of the applicable plan and stock option agreement. In general, in the event of a participant’s termination of service for any reason, unvested options are forfeited as of the date of such termination without any payment to the participant. The Company records share-based compensation expense only for those awards that are expected to vest and as such, the Company applies an estimated forfeiture rate at the time of grant and adjusts the forfeiture rate to reflect actual forfeitures quarterly. As of December 31, 2020, $15.1 million of total remaining unrecognized compensation cost related to unvested stock options, net of estimated forfeitures, is expected to be recognized over a weighted-average period of 2.7 years. Restricted Stock and Restricted Stock Units The Company grants restricted stock units (“RSUs”) to Company personnel and non-employee directors under the Company’s 2015 Plan (and prior to its approval, under the 2012 Plan) and 2012 Directors Plan, respectively. Prior to 2017, awards to non-employee directors were in the form of restricted stock. In addition, the Company has issued in the past, and may issue in the future, its equity securities to compensate employees of acquired businesses for future services. Equity-based awards granted in connection with acquisitions of businesses may be issued in the form of service-based awards requiring continuing employment with the Company, restricted stock subject to trading restrictions, and performance-based awards, which would vest only if certain specified performance and service conditions are met. The awards issued in connection with acquisitions of businesses are subject to the terms and conditions contained in the applicable award agreements and acquisition documents. Service-Based Awards The table below summarizes activity related to the Company’s equity-classified and liability-classified service-based awards for the years ended December 31, 2020, 2019 and 2018: Equity-Classified Equity-Classified Equity-Settled Restricted Stock Units Liability-Classified Cash-Settled Restricted Stock Units Number of Weighted Average Grant Date Number of Weighted Average Grant Date Number of Weighted Average Grant Date Unvested service-based awards outstanding as of January 1, 2018 2 $ 54.37 688 $ 71.60 315 $ 72.50 Awards granted — $ — 381 $ 115.84 85 $ 112.65 Awards modified — $ — (3) $ 80.27 3 $ 120.18 Awards vested (1) $ 47.76 (218) $ 70.10 (92) $ 72.69 Awards forfeited/cancelled — $ — (50) $ 86.97 (8) $ 81.40 Unvested service-based awards outstanding as of December 31, 2018 1 $ 63.10 798 $ 92.13 303 $ 83.99 Awards granted 9 $ 167.18 284 $ 170.29 56 $ 170.13 Awards modified — $ — 7 $ 170.74 1 $ 168.36 Awards vested — $ — (287) $ 87.79 (111) $ 80.51 Awards forfeited/cancelled — $ — (43) $ 114.45 (7) $ 94.77 Unvested service-based awards outstanding as of December 31, 2019 10 $ 162.96 759 $ 122.48 242 $ 105.40 Awards granted — $ — 294 $ 204.57 60 $ 181.77 Awards modified — $ — (1) $ 122.55 — $ — Awards vested (1) $ 63.10 (317) $ 108.87 (122) $ 91.39 Awards forfeited/cancelled — $ — (49) $ 148.11 (5) $ 113.94 Unvested service-based awards outstanding as of December 31, 2020 9 $ 167.18 686 $ 162.15 175 $ 141.16 The fair value of vested service-based awards (measured at the vesting date) for the years ended December 31, 2020, 2019 and 2018 was as follows: For the Years Ended December 31, 2020 2019 2018 Equity-classified equity-settled Restricted stock $ 101 $ 73 $ 142 Restricted stock units 60,042 48,111 24,987 Liability-classified cash-settled Restricted stock units 22,014 18,449 10,349 Total fair value of vested service-based awards $ 82,157 $ 66,633 $ 35,478 As of December 31, 2020, $0.8 million of total remaining unrecognized stock-based compensation costs related to service-based equity-classified restricted stock is expected to be recognized over the weighted-average remaining requisite service period of 1.7 years. During the year ended December 31, 2019, the Company issued 9 thousand shares of service-based restricted stock in connection with an acquisition of a business. See Note 2 “Acquisitions” for additional information regarding business acquisitions. As of December 31, 2020, $76.3 million of total remaining unrecognized stock-based compensation costs related to service-based equity-classified RSUs, net of estimated forfeitures, is expected to be recognized over the weighted-average remaining requisite service period of 2.7 years. During the years ended December 31, 2020 and 2019, in connection with business acquisitions, the Company issued 19 thousand and 22 thousand equity-classified RSUs, respectively. During the first quarter of 2020, in connection with a 2019 acquisition of a business, the Company formally issued 6 thousand equity-classified RSUs. See Note 2 “Acquisitions” for additional information regarding business acquisitions. As of December 31, 2020, $32.3 million of total remaining unrecognized stock-based compensation costs related to service-based liability-classified RSUs, net of estimated forfeitures, is expected to be recognized over the weighted-average remaining requisite service period of 2.3 years. During the years ended December 31, 2020 and 2019, the Company issued 10 thousand and 7 thousand shares, respectively, of service-based liability-classified cash-settled RSUs in connection with business acquisitions. See Note 2 “Acquisitions” for additional information regarding business acquisitions. The liability associated with the Company’s service-based liability-classified RSUs as of December 31, 2020 and 2019 was $26.8 million and $21.9 million, respectively, and is classified as Accrued compensation and benefits expenses in the consolidated balance sheets. Performance-Based Awards The table below summarizes activity related to the Company’s performance-based awards for the years ended December 31, 2020, 2019 and 2018: Equity-Classified Equity-Classified Number of Weighted Average Grant Date Number of Weighted Average Grant Date Unvested performance-based awards outstanding as of January 1, 2018 — $ — — $ — Awards granted — $ — 45 $ 121.75 Awards vested — $ — (8) $ 121.75 Awards forfeited/cancelled — $ — (7) $ 121.75 Unvested performance-based awards outstanding as of December 31, 2018 — $ — 30 $ 121.75 Awards granted 9 $ 165.87 — $ — Awards modified — $ — (30) $ 121.75 Unvested performance-based awards outstanding as of December 31, 2019 9 $ 165.87 — $ — Awards granted — $ — 31 $ 210.44 Awards vested — $ — (10) $ 177.81 Unvested performance-based awards outstanding as of December 31, 2020 9 $ 165.87 21 $ 227.16 During the year ended December 31, 2020, the Company agreed to issue RSUs at future dates in connection with 2020 acquisitions of businesses. The number of awards to be issued is subject to attainment of specified performance targets in the 2 years after the acquisition dates as well as the Company’s stock price at the time of formal issuance. See Note 2 “Acquisitions” in the consolidated financial statements for additional information regarding business acquisitions. The awards require continued service and vest over 3 years from the dates of acquisition. As of December 31, 2020, taking into consideration the probability of achieving the specified performance goals, $0.5 million of total remaining unrecognized stock-based compensation costs is expected to be recognized over the weighted-average remaining requisite service period of 2 years. If all performance criteria are met, these awards could be worth up to $11.5 million. During the year ended December 31, 2020, in connection with a 2019 acquisition of a business, the Company formally issued 25 thousand performance-based equity-classified RSUs. During the year ended December 31, 2020, 7 thousand performance-based equity-classified RSUs were granted in connection with 2020 acquisitions of businesses. See Note 2 “Acquisitions” in the consolidated financial statements for additional information regarding business acquisitions. As of December 31, 2020, $3.6 million of total remaining unrecognized stock-based compensation cost related to performance-based equity-classified RSUs is expected to be recognized over the weighted-average remaining requisite service period of 2.8 years. During the year ended December 31, 2019, the Company issued 9 thousand shares of performance-based equity-classified restricted stock in connection with an acquisition of a business. These awards contain a condition for attainment of specified performance targets in the 12 months after the acquisition date and require continued service through 4.0 years after the acquisition date. As of December 31, 2020, the performance targets were achieved in full and achievement of future vesting is exclusively dependent on continued service. See Note 2 “Acquisitions” for additional information regarding business acquisitions. As of December 31, 2020, $1.0 million of total remaining unrecognized stock-based compensation cost related to performance-based equity-classified restricted stock is expected to be recognized over the weighted-average remaining requisite service period of 2.7 years. Performance-based equity-classified RSUs were granted during the year ended December 31, 2018 in connection with the acquisition of Continuum with a variable vesting period, subject to satisfaction of the applicable performance conditions with each vesting portion having its own service inception date. Compensation was to be recognized over the vesting period and adjusted each period for the probability of achievement of the performance criteria for each vesting portion separately. During the fourth quarter of 2018, the Company accelerated the recognition of $0.8 million of expense due to vesting of performance-based equity-classified RSUs in accordance with the terms of the award agreement. During the year ended December 31, 2019, the Company and holders of the unvested performance-based equity-classified RSUs mutually agreed to cancel these awards and the Company issued service-based stock option and equity-classified RSU awards with four-year vesting terms to those same recipients. The fair value of vested performance-based awards (measured at the vesting date) for the years ended December 31, 2020, 2019 and 2018 was as follows: For the Years Ended December 31, 2020 2019 2018 Equity-classified equity-settled Restricted stock units $ 3,282 — $ 1,046 Total fair value of vested performance-based awards $ 3,282 $ — $ 1,046

INCOME TAXES

INCOME TAXES	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES Income Before Provision for Income Taxes Income before provision for income taxes based on geographic location is disclosed in the table below: For the Years Ended December 31, 2020 2019 2018 Income before provision for income taxes: United States $ 100,411 $ 65,370 $ 44,527 Foreign 278,068 234,156 205,246 Total $ 378,479 $ 299,526 $ 249,773 Provision for Income Taxes The provision for income taxes consists of the following: For the Years Ended December 31, 2020 2019 2018 Current Federal $ 19,249 $ 16,943 $ 10,814 State 7,022 3,610 4,123 Foreign 45,042 25,680 42,580 Deferred Federal (16,235) (9,425) (37,785) State (1,682) (358) (3,548) Foreign (2,077) 2,019 (6,667) Total $ 51,319 $ 38,469 $ 9,517 The U.S. Tax Act significantly changed U.S. corporate income tax laws including a reduction of the U.S. corporate income tax rate from 35.0% to 21.0% effective January 1, 2018 and the creation of a territorial tax system with a one-time transition tax on accumulated foreign subsidiary earnings not previously subject to U.S. income tax. In addition, the U.S. Tax Act created new taxes on certain foreign-sourced earnings and certain related party payments, which are referred to as GILTI and the base erosion and anti-abuse tax (“BEAT”), respectively. Due to the timing of the enactment and the complexity involved in applying the provisions of the U.S. Tax Act, the Company made reasonable estimates of the effects and recorded provisional amounts in its financial statements as of December 31, 2017. During the year ended December 31, 2018, the Company completed its analysis of the impact of the U.S. Tax Act and recorded the following adjustments to the recorded provisional amounts: • The one-time transition tax on accumulated foreign subsidiary earnings not previously subject to U.S. income tax requires the Company to pay U.S. income tax at a rate of 15.5% to the extent of foreign cash and certain other net current assets and 8.0% on the remaining earnings. During the year ended December 31, 2018, the Company completed its assessment and refined its estimate reducing the provisional charge recorded in 2017 by $4.9 million. As of December 31, 2020, the remaining unpaid balance of the one-time transition tax was $40.5 million to be paid in annual installments with the final payment due in 2025. • In 2018, the Company completed its remeasurement of its U.S. federal deferred tax assets and liabilities based on rates at which they are expected to reverse in the future, and consequently recorded an additional charge of $0.9 million to reduce its net deferred tax assets. Based on proposed tax regulations issued by the U.S. Department of the Treasury during 2018, the Company determined that a U.S. foreign tax credit could be claimed for withholding tax paid to Belarus in connection with dividends previously remitted, resulting in a net $4.9 million income tax benefit recognized during the year ended December 31, 2018. As of December 31, 2020, the Company had approximately $1,039.0 million of accumulated undistributed foreign earnings that are expected to be indefinitely reinvested. Due to the enactment of the U.S. Tax Act and the one-time transition tax on accumulated foreign subsidiary earnings, these accumulated foreign earnings are no longer expected to be subject to U.S. federal income tax if repatriated but could be subject to state and foreign income and withholding taxes. Effective Tax Rate Reconciliation The reconciliation of the provision for income taxes at the federal statutory income tax rate to the Company’s effective income tax rate is as follows: For the Years Ended December 31, 2020 2019 2018 Provision for income taxes at federal statutory rate $ 79,481 $ 62,898 $ 52,452 Increase/(decrease) in taxes resulting from: Impact from U.S. Tax Act — — (4,009) Entity classification election deferred tax asset impact — — (25,962) GILTI and BEAT U.S. taxes 191 (926) 1,526 Excess tax benefits relating to stock-based compensation (36,646) (28,385) (17,370) Subsidiary withholding tax liability and related foreign tax credit — — (4,850) Foreign tax expense and tax rate differential (387) (1,402) (88) Effect of permanent differences 3,507 3,264 2,724 State taxes, net of federal benefit 5,323 2,971 3,452 Stock-based compensation expense 44 571 652 Other (194) (522) 990 Provision for income taxes $ 51,319 $ 38,469 $ 9,517 The Company’s worldwide effective tax rate for the years ended December 31, 2020, 2019 and 2018 was 13.6%, 12.8% and 3.8%, respectively. The provision for income taxes in the year ended December 31, 2018 was favorably impacted by the recognition of $26.0 million of net deferred tax assets resulting from the Company’s decision to change the tax status and to classify most of its foreign subsidiaries as disregarded for U.S. income tax purposes. This change subjects the income of the disregarded foreign subsidiaries to U.S. income taxation. In addition, the Company recorded excess tax benefits upon vesting or exercise of stock-based awards of $36.6 million, $28.4 million and $17.4 million during the years ended December 31, 2020, 2019 and 2018, respectively. In Belarus, member technology companies of High-Technologies Park, including the Company’s local subsidiary, have a full exemption from Belarus income tax on qualifying income through January 2049. However, beginning February 1, 2018, the earnings of the Company’s Belarus local subsidiary became subject to U. S. income taxation due to the Company’s decision to change the tax status of the subsidiary. There was no aggregate dollar benefit derived from this tax holiday for the years ended December 31, 2020 and 2019, and the aggregate dollar benefits derived from this tax holiday approximated $1.4 million for the year ended December 31, 2018. There was no impact on diluted net income per share for the years ended December 31, 2020 and 2019. The benefit the tax holiday had on diluted net income per share approximated $0.02 for the year ended December 31, 2018. Deferred Income Taxes Deferred income taxes reflect the net effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. Significant components of the Company’s deferred tax assets and liabilities are as follows: As of December 31, 2020 As of December 31, 2019 Deferred tax assets: Property and equipment $ 8,164 $ 5,329 Intangible assets 827 574 Accrued expenses 50,639 41,457 Net operating loss carryforward 6,089 5,168 Deferred revenue 9,796 3,510 Stock-based compensation 30,112 29,596 Operating lease liabilities 51,519 7,438 Foreign tax credit 2,168 3,491 Foreign currency exchange 4,890 2,499 Other assets 1,252 1,533 Deferred tax assets $ 165,456 $ 100,595 Less: valuation allowance (5,485) (3,877) Total deferred tax assets $ 159,971 $ 96,718 Deferred tax liabilities: Property and equipment $ 3,818 $ 4,981 Intangible assets 12,018 11,364 Operating lease right-of-use assets 50,149 6,900 Accrued revenue and expenses 991 2,176 U.S. taxation of foreign subsidiaries 1,608 — Foreign currency exchange 1,153 375 Other liabilities 1,095 437 Total deferred tax liabilities $ 70,832 $ 26,233 Net deferred tax assets $ 89,139 $ 70,485 As of December 31, 2020 and 2019, the Company classified $3.3 million and $4.5 million, respectively, of deferred tax liabilities as Other noncurrent liabilities in the consolidated balance sheets. Included in the stock-based compensation expense deferred tax asset at December 31, 2020 and 2019 is $6.1 million and $6.8 million, respectively, that is related to acquisitions and is amortized for tax purposes over a 10 to 15-year period. As of December 31, 2020, the Company’s domestic and foreign net operating loss (“NOL”) carryforwards for income tax purposes were approximately $4.7 million and $22.5 million, respectively. If not utilized, the domestic NOL carryforwards will begin to expire in 2021. The foreign NOL carryforwards include $6.6 million from jurisdictions with no expiration date, with the remainder expiring as follows: $5.7 million in 2021, $5.5 million in 2022, $0.9 million in 2023, $1.7 million in 2024, $2.1 million in 2025. The Company maintains a valuation allowance primarily related to the net operating loss carryforwards in certain foreign jurisdictions that the Company believes are not likely to be realized, which totaled $22.4 million as of December 31, 2020. Unrecognized Tax Benefits As of December 31, 2020 and 2019, unrecognized tax benefits of $3.3 million and $2.9 million, respectively, are included in Income taxes payable, noncurrent within the consolidated balance sheets. During the year ended December 31, 2020, a new uncertain tax position resulted in an unrecognized tax benefit of $0.8 million, and reversals related to prior year tax positions yielded a tax benefit of $0.5 million. There were no significant new tax positions that resulted in unrecognized tax benefits or reversals related to prior year tax positions during the years ended December 31, 2019 and 2018. There were no tax positions for which it was reasonably possible that unrecognized tax benefits will significantly increase or decrease within twelve months of the reporting date. The Company is subject to taxation in the United States and various states and foreign jurisdictions including Russia, Germany, Ukraine, the United Kingdom, Hungary, Switzerland, Netherlands, Poland and India. With few exceptions, as of December 31, 2020, the Company is no longer subject to U.S. federal, state, local or foreign examinations by tax authorities for years before 2016.

EARNINGS PER SHARE

EARNINGS PER SHARE	12 Months Ended
	Dec. 31, 2020
Earnings Per Share [Abstract]
EARNINGS PER SHARE	EARNINGS PER SHARE Basic earnings per share is computed by dividing net income available to common shareholders by the weighted-average number of shares of common stock outstanding during the period. For purposes of computing basic earnings per share, any nonvested shares of restricted stock that have been issued by the Company and are contingently returnable to the Company are excluded from the weighted-average number of shares of common stock outstanding during the period. Diluted earnings per share is computed by dividing net 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 equity-settled RSUs. The dilutive effect of potentially dilutive securities is reflected in diluted earnings per share by application of the treasury stock method. The following table sets forth the computation of basic and diluted earnings per share of common stock as follows: For the Years Ended December 31, 2020 2019 2018 Numerator for basic and diluted earnings per share: Net income $ 327,160 $ 261,057 $ 240,256 Numerator for basic and diluted earnings per share $ 327,160 $ 261,057 $ 240,256 Denominator: Weighted average common shares for basic earnings per share 55,727 54,719 53,623 Net effect of dilutive stock options, restricted stock units and restricted stock awards 2,719 2,949 3,050 Weighted average common shares for diluted earnings per share 58,446 57,668 56,673 Net Income per share: Basic $ 5.87 $ 4.77 $ 4.48 Diluted $ 5.60 $ 4.53 $ 4.24

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	12 Months Ended
	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES Indemnification Obligations — In the normal course of business, the Company is a party to a variety of agreements under which it may be obligated to indemnify the other party for certain matters. These obligations typically arise in contracts where the Company customarily agrees to hold the other party harmless against losses arising from a breach of representations or covenants for certain matters, infringement of third party intellectual property rights, data privacy violations, and certain tortious conduct in the course of providing services. The duration of these indemnifications varies, and in certain cases, is indefinite. The Company is unable to reasonably estimate the maximum potential amount of future payments under these or similar agreements due to the unique facts and circumstances of each agreement and the fact that certain indemnifications provide for no limitation to the maximum potential future payments under the indemnification. Management is not aware of any such matters that would have a material effect on the consolidated financial statements of the Company. Litigation — From time to time, the Company is involved in litigation, claims or other contingencies arising in the ordinary course of business. The Company accrues a liability when a loss is considered probable and the amount can be reasonably estimated. When a material loss contingency is reasonably possible but not probable, the Company does not record a liability, but instead discloses the nature and the amount of the claim, and an estimate of the loss or range of loss, if such an estimate can be made. Legal fees are expensed as incurred. In the opinion of management, the outcome of any existing claims and legal or regulatory proceedings, if decided adversely, is not expected to have a material effect on the Company’s business, financial condition, results of operations or cash flows. Building Acquisition Commitment —During the year ended December 31, 2019, the Company entered into an agreement to purchase office space in Ukraine intended to support the global delivery center in that country. The agreement is subject to completion of construction and other ordinary closing conditions. As of December 31, 2020, the Company has committed to making future payments totaling approximately $36.9 million including VAT to the sellers upon transfer of the building.

SEGMENT INFORMATION

SEGMENT INFORMATION	12 Months Ended
	Dec. 31, 2020
Segment Reporting [Abstract]
SEGMENT INFORMATION	SEGMENT INFORMATION The Company determines its business segments and reports segment information in accordance with how the Company’s chief operating decision maker (“CODM”) organizes the segments to evaluate performance, allocate resources and make business decisions. Segment results are based on the segment’s revenues and operating profit, where segment operating profit is defined as income from operations before unallocated costs. Expenses included in segment operating profit consist principally of direct selling and delivery costs as well as an allocation of certain shared services expenses. Certain corporate expenses are not allocated to specific segments as these expenses are not controllable at the segment level. Such expenses include certain types of professional fees, certain taxes included in operating expenses including the Belarus High-Technologies Park membership fee, compensation to non-employee directors and certain other general and administrative expenses, including compensation of specific groups of non-production employees. In addition, the Company does not allocate amortization of intangible assets acquired through business combinations, goodwill and other asset impairment charges, stock-based compensation expenses, acquisition-related costs and certain other one-time charges. These unallocated amounts are combined with total segment operating profit to arrive at consolidated income from operations as reported below in the reconciliation of segment operating profit to consolidated income before provision for income taxes. Additionally, management has determined that it is not practical to allocate identifiable assets by segment since such assets are used interchangeably among the segments. The Company manages its business primarily based on the managerial responsibility for its client base and market. As managerial responsibility for a particular customer relationship generally correlates with the customer’s geographic location, there is a high degree of similarity between customer locations and the geographic boundaries of the Company’s reportable segments. In some cases, managerial responsibility for a particular customer is assigned to a management team in another region and is usually based on the strength of the relationship between customer executives and particular members of EPAM’s senior management team. In such cases, the customer’s activity would be reported through the respective management team member’s reportable segment. Revenues from external customers and operating profit, before unallocated expenses, by reportable segments were as follows: For the years ended December 31, 2020 2019 2018 Segment revenues: North America $ 1,601,820 $ 1,380,944 $ 1,076,979 Europe 947,305 820,717 692,785 Russia 110,353 92,137 73,148 Total revenues $ 2,659,478 $ 2,293,798 $ 1,842,912 Segment operating profit: North America $ 345,196 $ 293,757 $ 221,846 Europe 152,902 114,863 115,876 Russia 5,811 17,347 11,377 Total segment operating profit $ 503,909 $ 425,967 $ 349,099 Intersegment transactions were excluded from the above on the basis that they are neither included in the measure of a segment’s profit and loss results, nor considered by the CODM during the review of segment results. There were no customers individually exceeding 10% of our total segment revenues for the years ended December 31, 2020, 2019 and 2018. Reconciliation of segment operating profit to consolidated income before provision for income taxes is presented below: For the Years Ended December 31, 2020 2019 2018 Total segment operating profit: $ 503,909 $ 425,967 $ 349,099 Unallocated costs: Stock-based compensation expense (75,238) (72,036) (59,188) Amortization of purchased intangibles (12,340) (9,914) (8,101) Other acquisition-related expenses (1,868) (3,774) (916) Other unallocated costs (35,139) (37,393) (35,130) Income from operations 379,324 302,850 245,764 Interest and other income, net 3,822 8,725 3,522 Foreign exchange (loss)/gain (4,667) (12,049) 487 Income before provision for income taxes $ 378,479 $ 299,526 $ 249,773 Geographic Area Information Long-lived assets include property and equipment, net of accumulated depreciation and amortization, and management has determined that it is not practical to allocate these assets by segment since such assets are used interchangeably among the segments. Physical locations and values of the Company’s long-lived assets are presented below: As of December 31, 2020 As of December 31, 2019 As of December 31, 2018 Belarus $ 73,988 $ 75,984 $ 50,085 Ukraine 30,980 24,652 8,433 United States 15,718 15,637 13,101 Russia 15,036 17,980 9,902 India 7,079 7,443 7,019 Poland 5,434 5,029 2,637 Hungary 5,365 5,201 3,168 Spain 2,799 1,106 875 China 2,722 3,036 2,651 Mexico 2,419 2,353 812 Other 7,993 6,838 3,963 Total $ 169,533 $ 165,259 $ 102,646 The table below presents the Company’s revenues by customer location for the years ended December 31, 2020, 2019 and 2018: For the Years Ended December 31, 2020 2019 2018 United States $ 1,523,731 $ 1,321,662 $ 1,029,327 United Kingdom 331,217 290,039 200,918 Switzerland 203,391 152,710 144,398 Netherlands 114,678 88,488 70,274 Russia 104,846 89,941 71,181 Germany 84,902 82,441 80,787 Canada 68,416 68,304 69,836 Other locations 228,297 200,213 176,191 Revenues $ 2,659,478 $ 2,293,798 $ 1,842,912

ACCUMULATED OTHER COMPREHENSIVE

ACCUMULATED OTHER COMPREHENSIVE LOSS	12 Months Ended
	Dec. 31, 2020
Equity [Abstract]
ACCUMULATED OTHER COMPREHENSIVE LOSS	ACCUMULATED OTHER COMPREHENSIVE LOSS The following table summarizes the changes in the accumulated balances for each component of accumulated other comprehensive loss: For the Years Ended December 31, 2020 2019 2018 Foreign currency translation Beginning balance $ (32,666) $ (38,961) $ (17,623) Foreign currency translation 5,802 7,912 (25,097) Income tax (expense)/benefit (1,304) (1,617) 3,759 Foreign currency translation, net of tax 4,498 6,295 (21,338) Ending balance $ (28,168) $ (32,666) $ (38,961) Cash flow hedging instruments Beginning balance $ 1,292 $ (2,553) $ — Unrealized gain in fair value 8,076 2,933 867 Net (loss)/gain reclassified into Cost of revenues (exclusive of depreciation and amortization) (5,031) 2,028 (4,161) Income tax (expense)/benefit (695) (1,116) 741 Cash flow hedging instruments, net of tax 2,350 3,845 (2,553) Ending balance (1) $ 3,642 $ 1,292 $ (2,553) Defined benefit plans Beginning balance $ — $ — $ — Actuarial losses (1,275) — — Income tax benefit 289 — — Defined benefit plans, net of tax (986) — — Ending balance $ (986) $ — $ — Accumulated other comprehensive loss $ (25,512) $ (31,374) $ (41,514) (1) As of December 31, 2020, the ending balance of net unrealized gains related to derivatives designated as cash flow hedges is expected to be reclassified into Cost of revenues (exclusive of depreciation and amortization) in the next twelve months.

QUARTERLY FINANCIAL DATA (UNAUD

QUARTERLY FINANCIAL DATA (UNAUDITED)	12 Months Ended
	Dec. 31, 2020
Quarterly Financial Information Disclosure [Abstract]
QUARTERLY FINANCIAL DATA (UNAUDITED)	QUARTERLY FINANCIAL DATA (UNAUDITED) Summarized quarterly results for the years ended December 31, 2020 and 2019 were as follows: Three Months Ended 2020 March 31 June 30 September 30 December 31 Full Year Revenues $ 651,359 $ 632,383 $ 652,243 $ 723,493 $ 2,659,478 Operating expenses: Cost of revenues (exclusive of depreciation and amortization) 423,802 419,540 423,388 465,792 1,732,522 Selling, general and administrative expenses 125,108 114,191 116,530 128,929 484,758 Depreciation and amortization expense 14,940 15,226 15,929 16,779 62,874 Income from operations 87,509 83,426 96,396 111,993 379,324 Interest and other income/(expense), net 2,386 1,817 1,672 (2,053) 3,822 Foreign exchange gain/(loss) 6,524 (9,167) 5,896 (7,920) (4,667) Income before provision for income taxes 96,419 76,076 103,964 102,020 378,479 Provision for income taxes 10,854 9,452 14,532 16,481 51,319 Net income $ 85,565 $ 66,624 $ 89,432 $ 85,539 $ 327,160 Comprehensive income $ 47,678 $ 85,512 $ 89,133 $ 110,699 $ 333,022 Basic net income per share (1) $ 1.55 $ 1.20 $ 1.60 $ 1.53 $ 5.87 Diluted net income per share (1) $ 1.47 $ 1.14 $ 1.53 $ 1.46 $ 5.60 (1) Earnings per share amounts for each quarter may not necessarily total to the yearly earnings per share due to the weighting of shares outstanding on a quarterly and year to date basis. Three Months Ended 2019 March 31 June 30 September 30 December 31 Full Year Revenues $ 521,333 $ 551,587 $ 588,103 $ 632,775 $ 2,293,798 Operating expenses: Cost of revenues (exclusive of depreciation and amortization) 344,689 355,915 377,525 410,069 1,488,198 Selling, general and administrative expenses 101,786 111,762 118,886 124,999 457,433 Depreciation and amortization expense 10,200 11,028 11,127 12,962 45,317 Income from operations 64,658 72,882 80,565 84,745 302,850 Interest and other income, net 3,076 1,190 2,509 1,950 8,725 Foreign exchange loss (3,484) (3,562) (3,105) (1,898) (12,049) Income before provision for income taxes 64,250 70,510 79,969 84,797 299,526 Provision for income taxes 3,496 11,733 12,967 10,273 38,469 Net income $ 60,754 $ 58,777 $ 67,002 $ 74,524 $ 261,057 Comprehensive income $ 66,797 $ 62,934 $ 54,725 $ 86,741 $ 271,197 Basic net income per share (1) $ 1.12 $ 1.07 $ 1.22 $ 1.35 $ 4.77 Diluted net income per share (1) $ 1.06 $ 1.02 $ 1.16 $ 1.29 $ 4.53 (1) Earnings per share amounts for each quarter may not necessarily total to the yearly earnings per share due to the weighting of shares outstanding on a quarterly and year to date basis.

VALUATION AND QUALIFYING ACCOUN

VALUATION AND QUALIFYING ACCOUNTS	12 Months Ended
	Dec. 31, 2020
SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract]
VALUATION AND QUALIFYING ACCOUNTS	VALUATION AND QUALIFYING ACCOUNTS FOR THE YEARS ENDED DECEMBER 31, 2020, 2019 AND 2018 (In thousands) Balance at Additions Deductions/ Balance at End of Year Year Ended December 31, 2020 Allowance for doubtful accounts for trade receivables and contract assets $ 3,210 3,282 (1,606) $ 4,886 Valuation allowance on deferred tax assets $ 3,877 1,608 — $ 5,485 Year Ended December 31, 2019 Allowance for doubtful accounts for trade receivables and contract assets $ 1,557 2,072 (419) $ 3,210 Valuation allowance on deferred tax assets $ 3,189 688 — $ 3,877 Year Ended December 31, 2018 Allowance for doubtful accounts for trade receivables and contract assets $ 1,186 2,722 (2,351) $ 1,557 Valuation allowance on deferred tax assets $ 924 2,265 — $ 3,189

BUSINESS AND SUMMARY OF SIGNI_2

BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Nature of Operations	EPAM Systems, Inc. (the “Company” or “EPAM”) is a leading global provider of digital platform engineering and software development services to customers located around the world, primarily in North America, Europe, Asia and Australia. The Company’s industry expertise includes financial services, travel and consumer, software and hi-tech, business information and media, life sciences and healthcare, as well as other emerging industries. The Company is incorporated in Delaware with headquarters in Newtown, Pennsylvania.
Principles of Consolidation	Principles of Consolidation — The consolidated financial statements include the financial statements of EPAM and its subsidiaries. All intercompany balances and transactions have been eliminated.
Reclassifications	Reclassifications — Certain amounts recorded in the prior-period consolidated balance sheets and consolidated statements of cash flows presented have been reclassified to conform to the current-period financial statement presentation. These reclassifications had no effect on previously reported results of operations .
Use of Estimates	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.
Cash and Cash Equivalents	Cash and Cash Equivalents — Cash equivalents are short-term, highly liquid investments and deposits that are readily convertible into cash, with maturities of three months or less at the date acquired. Highly liquid investments with maturities greater than three months at the date acquired are reported separately from cash equivalents.
Accounts Receivable	Trade Receivables and Contract Assets — The Company classifies its right to consideration in exchange for deliverables as either a trade receivable or a contract asset. A trade receivable is a right to consideration that is unconditional (i.e., only the passage of time is required before payment is due) regardless of whether the amounts have been billed. Trade receivables are stated net of allowance for doubtful accounts. Outstanding trade receivables are reviewed periodically and allowances are provided for the estimated amount of receivables that may not be collected. The allowance for doubtful accounts is determined based on historical experience and management’s evaluation of trade receivables. A contract asset is a right to consideration that is conditional upon factors other than the passage of time. Contract assets primarily relate to unbilled amounts on fixed-price contracts. Contract assets are recorded when services have been provided but the Company does not have an unconditional right to receive consideration. The Company recognizes an impairment loss when the contract carrying amount is greater than the remaining consideration receivable, less directly related costs to be incurred.
Property and Equipment	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.
Business Combinations	Business Combinations — The Company accounts for business combinations using the acquisition method which requires it to estimate the fair value of identifiable assets acquired and liabilities assumed, including any contingent consideration, to properly allocate the purchase price to the individual assets acquired and liabilities assumed in accordance with the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) Topic 805, Business Combinations . The allocation of the purchase price utilizes significant estimates in determining the fair values of identifiable assets acquired and liabilities assumed, especially with respect to intangible assets. The significant estimates and assumptions used include the timing and amount of forecasted revenues and cash flows, anticipated growth rates, customer attrition rates, the discount rate reflecting the risk inherent in future cash flows and the determination of useful lives for finite-lived assets. 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. The acquired assets typically include customer relationships, software, trade names, non-competition agreements, and assembled workforce and as a result, a substantial portion of the purchase price is allocated to goodwill and other intangible assets.
Long-Lived Assets	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.
Goodwill and Other Indefinite-Lived Intangible Assets	Goodwill and Other Indefinite-Lived Intangible Assets — Goodwill and other intangible assets that have indefinite useful lives are accounted for in accordance with 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.
Derivative Financial Instruments	Derivative Financial Instruments — The Company enters into derivative financial instruments to manage exposure to fluctuations in certain foreign currencies. During 2018, for accounting purposes, these foreign currency forward contracts became designated as hedges, as defined under FASB ASC Topic 815, Derivatives and Hedging . The Company measures these foreign currency derivative contracts at fair value on a recurring basis utilizing Level 2 inputs and recognizes them as either assets or liabilities in its consolidated balance sheets. The Company records changes in the fair value of these hedges in accumulated other comprehensive income/(loss) until the forecasted transaction occurs. When the forecasted transaction occurs, the Company reclassifies the related gain or loss on the cash flow hedge to cost of revenues (exclusive of depreciation and amortization). In the event the underlying forecasted transaction does not occur, or it becomes probable that it will not occur, the Company reclassifies the gain or loss on the underlying hedge into income. If the Company does not elect hedge accounting, or the contract does not qualify for hedge accounting treatment, the changes in fair value from period to period are recorded in income. The cash flow impact of derivatives identified as hedging instruments is reflected as cash flows from operating activities. The cash flow impact of derivatives not identified as hedging instruments is reflected as cash flows from investing activities.
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 FASB 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. Changes in the fair value of liabilities could cause a material impact to, and volatility in the Company’s operating results. See Note 4 “Fair Value Measurements.”
Accumulated Other Comprehensive Income	Accumulated Other Comprehensive Loss — Accumulated other comprehensive loss (“AOCI”) consists of changes in the cumulative foreign currency translation adjustments and actuarial gains and losses on defined benefit pension plans. In addition, the Company enters into foreign currency exchange contracts, which are designated as cash flow hedges in accordance with FASB ASC Topic 815, Derivatives and Hedging.
Revenue Recognition	Revenue Recognition — Effective January 1, 2018, the Company adopted the Accounting Standard Update (“ASU”) No. 2014-09, Revenue from Contracts with Customers (Topic 606) as amended using the modified retrospective method. The standard effectively replaced previously existing revenue recognition guidance (Topic 605) and requires entities to recognize revenue to depict the transfer of promised goods or services in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services as well as requires additional disclosure about the nature, amount, timing and uncertainty of revenues and cash flows arising from customer contracts, including significant judgments and changes in judgments. The Company applied a practical expedient to aggregate the effect of all contract modifications that occurred before the adoption date. The following table summarizes the impacts of changes in accounting policies after adoption of Topic 606 on the Company’s consolidated Statement of Income for the year ended December 31, 2018, which primarily resulted from deferring the timing of revenue recognition for contracts that were previously recognized on a cash basis and recognizing revenues from certain license agreements at a point-in-time rather than over time: Year Ended December 31, 2018 As Reported Balances Without Adoption of Topic 606 Effect of Change Higher/(Lower) Revenues $ 1,842,912 $ 1,843,159 $ (247) Income from operations $ 245,764 $ 246,011 $ (247) Provision for income taxes $ 9,517 $ 9,572 $ (55) Net income $ 240,256 $ 240,448 $ (192) The Company recognizes revenues when control of goods or services is passed to a customer in an amount that reflects the consideration the Company expects to be entitled to in exchange for those goods or services. Such control may be transferred over time or at a point in time depending on satisfaction of obligations stipulated by the contract. Consideration expected to be received may consist of both fixed and variable components and is allocated to each separately identifiable performance obligation based on the performance obligation’s relative standalone selling price. Variable consideration usually takes the form of volume-based discounts, service level credits, price concessions or incentives. Determining the estimated amount of such variable consideration involves assumptions and judgment that can have an impact on the amount of revenues reported. The Company derives revenues from a variety of service arrangements, which have been evolving to provide more customized and integrated solutions to customers by combining software engineering with customer experience design, business consulting and technology innovation services. Fees for these contracts may be in the form of time-and-materials or fixed-price arrangements. The Company generates the majority of its revenues under time-and-material contracts, which are billed using hourly, daily or monthly rates to determine the amounts to be charged directly to the customer. The Company applies a practical expedient and revenues related to time-and-material contracts are recognized based on the right to invoice for services performed. Fixed-price contracts include maintenance and support arrangements which may exceed one year in duration. Maintenance and support arrangements generally relate to the provision of ongoing services and revenues for such contracts are recognized ratably over the expected service period. Fixed-price contracts also include application development arrangements, where progress towards satisfaction of the performance obligation is measured using input or output methods and input methods are used only when there is a direct correlation between hours incurred and the end product delivered. Assumptions, risks and uncertainties inherent in the estimates used to measure progress could affect the amount of revenues, receivables and deferred revenues at each reporting period. Revenues from licenses which have significant stand-alone functionality are recognized at a point in time when control of the license is transferred to the customer. Revenues from licenses which do not have stand-alone functionality are recognized over time.
Cost of Revenues (Exclusive of Depreciation and Amortization)	Cost of Revenues (Exclusive of Depreciation and Amortization) — Consists principally of salaries, bonuses, fringe benefits, stock-based compensation, project related travel costs and fees for subcontractors that are assigned to customer projects. Salaries and other compensation expenses of the Company’s delivery professionals are reported as cost of revenues regardless of whether the employees are actually performing customer services during a given period.
Selling, General and Administrative Expenses	Selling, General and Administrative Expenses — Consists of expenses associated with promoting and selling the Company’s services and general and administrative functions of the business. These expenses include the costs of salaries, bonuses, fringe benefits, stock-based compensation, severance, bad debt, travel, legal and accounting services, insurance, facilities including operating leases, advertising and other promotional activities. In addition, the Company pays a membership fee of 1% of revenues generated in Belarus to the administrative organization of the Belarus High-Technologies Park.
Stock-based Compensation	Stock-Based Compensation — The Company recognizes the cost of its equity settled stock-based incentive awards based on the fair value of the award at the date of grant, net of estimated forfeitures. The cost is generally expensed evenly over the service period, unless otherwise specified by the award agreement. The service period is the period over which the employee performs the related services, which is normally the same as the vesting period. Equity-based awards that do not require future service are expensed immediately. Quarterly, the forfeiture assumption is adjusted and such adjustment may affect the timing of recognition of the total amount of expense recognized over the vesting period. Stock-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.
Income Taxes	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. A 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.
Earnings Per Share (EPS)	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 by 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.
Foreign Currency Transaction	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).
Risks and Uncertainties	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, cash equivalents, short-term investments and trade receivables. The Company maintains cash, cash equivalents and short-term investments with financial institutions. The Company believes its credit policies reflect normal industry terms and business risk and there is no expectation of non-performance by the counterparties. The Company has cash in banks in Belarus, Russia, Ukraine, Kazakhstan, Armenia, Georgia and Uzbekistan, where the banking sector remains subject to periodic instability. Banking and other financial systems generally do not meet the banking standards of more developed markets, and bank deposits made by corporate entities are not insured. As of December 31, 2020, $146.2 million of total cash was kept in banks in these countries, of which $52.9 million was held in Belarus. In this region, and particularly in Belarus, a banking crisis, bankruptcy or insolvency of banks that process or hold the Company’s funds, may result in the loss of deposits or adversely affect the Company’s ability to complete banking transactions in the region, which could adversely affect the Company’s business and financial condition. Cash in this region is used for the operational needs of the local entities and cash balances change with the operating needs of these entities. The Company regularly monitors cash held in these countries and, to the extent the cash held exceeds amounts required to support its operations in these countries, the Company distributes the excess funds into markets with more developed banking sectors. Trade receivables are generally dispersed across many customers operating in different industries; therefore, concentration of credit risk is limited. Historically, credit losses and write-offs of trade receivables have not been material to the consolidated financial statements. If any of our customers enter bankruptcy protection or otherwise take steps to alleviate their financial distress, including distress resulting from the COVID-19 pandemic, the Company’s credit losses and write-offs of trade receivables could increase, which would negatively impact its results of operations. Foreign currency risk — The Company’s global operations are conducted predominantly in U.S. dollars. Other than U.S. dollars, the Company generates revenues in various currencies, principally, euros, British pounds, Russian rubles, Swiss francs, and Canadian dollars and incurs expenditures principally in Russian rubles, Polish zlotys, euros, Swiss francs, Hungarian forints, British pounds, Indian rupees, Chinese yuan renminbi and Mexican pesos. 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 trade receivables 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 are used materially in the Company’s business, appreciate or depreciate against the U.S. dollar. The Company has a hedging program whereby it entered into a series of foreign exchange forward contracts with durations of twelve months or less that are designated as cash flow hedges of forecasted Russian ruble, Polish zloty and Indian rupee transactions.
Adoption of New/ Pending Accounting Standards	Adoption of New Accounting Standards Unless otherwise discussed below, the adoption of new accounting standards did not have a material impact on the Company’s consolidated financial position, results of operations, and cash flows. Measurement of Credit Losses on Financial Instruments — In June 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. The amendments in this update changed how companies measure and recognize credit impairment for many financial assets. The new credit loss model requires companies to immediately recognize an estimate of credit losses expected to occur over the remaining life of the financial assets (including trade receivables) that are in the scope of the update. The update also made amendments to the current impairment model for held-to-maturity and available-for-sale debt securities and certain guarantees. The Company adopted Topic 326, effective January 1, 2020, using a modified-retrospective approach through a cumulative effect adjustment to retained earnings as of the beginning of the period of adoption. As a result of the adoption of Topic 326, the Company recorded an immaterial reduction to its allowance for doubtful accounts for trade receivables and contract assets . Leases — In February 2016, the FASB issued ASU 2016-02, Leases (“Topic 842”). The standard supersedes previously existing lease guidance (Topic 840) and requires entities to recognize all leases, with the exception of leases with a term of twelve months or less, on the balance sheet as right-of-use assets (“RoU Assets”) and lease liabilities. The guidance also changes disclosure requirements with a focus on providing information that will enable users of financial statements to assess the amount, timing and uncertainty of cash flows arising from leases. The Company adopted Topic 842, effective January 1, 2019, using the optional transition approach, which allows the Company to apply the provisions of the standard at the effective date without adjusting the comparable periods and carry forward disclosures under previously existing guidance for those periods presented within the Company’s financial statements. The Company determines if an arrangement is a lease or contains a lease at inception. The Company performs an assessment and classifies the lease as either an operating lease or a financing lease at the lease commencement date with a right-of-use asset and a lease liability recognized in the consolidated balance sheet under both classifications. The Company does not have finance leases that are material to the Company’s consolidated financial statements. Lease liabilities are initially measured at the present value of lease payments not yet paid. The present value is determined by applying the readily determinable rate implicit in the lease or, if not available, the incremental borrowing rate of the lessee. The Company determines the incremental borrowing rate of the lessee on a lease-by-lease basis by developing an estimated centralized U.S. dollar borrowing rate for a fully collateralized obligation with a term similar to the lease term and adjusts the rate to reflect the incremental risk associated with the foreign currency in which the lease is denominated. The development of this estimate includes the use of recovery rates, U.S. risk-free rates, foreign currency/country base rate yields, and a synthetic corporate credit rating of the Company developed using regression analysis. Lease agreements of the Company may include options to extend or terminate the lease and the Company includes such options in the lease term when it is reasonably certain that the Company will exercise that option. RoU Assets are recognized based on the initial measurement of the lease liabilities plus initial direct costs less lease incentives and, according to the guidance for long-lived assets, RoU Assets are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Lease expense for operating leases is recognized on a straight-line basis over the lease term. The Company elected a practical expedient to account for lease and non-lease components together as a single lease component. The Company also elected the short-term lease recognition exemption for all classes of lease assets with an original term of twelve months or less. As part of the transition, the Company elected a package of practical expedients allowing it to carry forward historical accounting for any expired or existing contracts that are or contain lease contracts, including classification of such contracts and initial direct costs associated with them. The adoption of Topic 842 on January 1, 2019 resulted in the recognition of RoU Assets for operating leases of $177.6 million and operating lease liabilities of $173.9 million. The adoption of Topic 842 did not have a material impact on the consolidated statement of income and comprehensive income, consolidated statement of changes in stockholders’ equity or the consolidated statement of cash flows. See Note 8 “Leases” in the condensed consolidated financial statements for additional information regarding leases. Pending Accounting Standards From time to time, new accounting pronouncements are issued by the FASB or other standards-setting bodies that the Company will adopt according to the various timetables the FASB specifies. The Company believes the impact of recently issued standards that are not yet effective will not have a material impact on its consolidated financial position, results of operations and cash flows upon adoption.

FAIR VALUE MEASUREMENTS (Polici

FAIR VALUE MEASUREMENTS (Policies)	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Non-Marketable Securities Without Readily Determinable Fair Values	The Company holds investments in equity securities that do not have readily determinable fair values. These investments are recorded at cost and are remeasured to fair value based on certain observable price changes or impairment events as they occur.

BUSINESS AND SIGNIFICANT ACCOUN

BUSINESS AND SIGNIFICANT ACCOUNTING POLICIES (Tables)	12 Months Ended
	Dec. 31, 2020
Topic 606
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Impact of Changes in Accounting Policies after Adoption of ASU	The following table summarizes the impacts of changes in accounting policies after adoption of Topic 606 on the Company’s consolidated Statement of Income for the year ended December 31, 2018, which primarily resulted from deferring the timing of revenue recognition for contracts that were previously recognized on a cash basis and recognizing revenues from certain license agreements at a point-in-time rather than over time: Year Ended December 31, 2018 As Reported Balances Without Adoption of Topic 606 Effect of Change Higher/(Lower) Revenues $ 1,842,912 $ 1,843,159 $ (247) Income from operations $ 245,764 $ 246,011 $ (247) Provision for income taxes $ 9,517 $ 9,572 $ (55) Net income $ 240,256 $ 240,448 $ (192)

ACQUISITIONS (Tables)

ACQUISITIONS (Tables)	12 Months Ended
	Dec. 31, 2020
Business Combinations [Abstract]
Fair Values of Assets Acquired and Liabilities Assumed	The following table summarizes the estimated fair values of the assets acquired and liabilities assumed as of the date of acquisition as updated for any changes as of December 31, 2019 for Continuum and Think and as of December 31, 2020 for test IO: Continuum Think test IO Cash and cash equivalents $ 2,251 $ 2,344 $ 663 Trade receivables and contract assets 9,139 2,637 621 Prepaid and other current assets 936 900 150 Goodwill 26,617 20,477 11,926 Intangible assets 14,450 6,882 6,219 Property and equipment and other noncurrent assets 8,902 1,214 305 Total assets acquired $ 62,295 $ 34,454 $ 19,884 Accounts payable, accrued expenses and other current liabilities $ 3,746 $ 2,025 $ 993 Long-term debt (Note 9) 3,220 — — Other noncurrent liabilities 490 — 1,568 Total liabilities assumed $ 7,456 $ 2,025 $ 2,561 Net assets acquired $ 54,839 $ 32,429 $ 17,323
Fair Values and Useful Lives of Intangible Assets Acquired	The following table presents the estimated fair values and useful lives of intangible assets acquired from Continuum, Think, and test IO as of the date of acquisition and updated for any changes during the years ended December 31, 2019 for Continuum and Think and December 31, 2020 for test IO: Continuum Think test IO Weighted Average Useful Life (in years) Amount Weighted Average Useful Life (in years) Amount Weighted Average Useful Life (in years) Amount Customer relationships 6.5 $ 5,800 7 $ 6,117 7 $ 2,456 Favorable lease 11.2 5,500 — — — — Software — — — — 6 3,461 Contract royalties 8 1,900 — — — — Trade names 5 1,250 5 765 4 302 Total $ 14,450 $ 6,882 $ 6,219

GOODWILL AND INTANGIBLE ASSET_2

GOODWILL AND INTANGIBLE ASSETS, NET (Tables)	12 Months Ended
	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill By Reportable Segment	Goodwill by reportable segment was as follows: North America Europe Russia Total Balance as of January 1, 2019 $ 103,542 $ 63,290 $ — $ 166,832 test IO acquisition (Note 2) 3,301 8,849 — 12,150 Other 2019 Acquisitions (Note 2) 6,503 9,546 738 16,787 Think purchase accounting adjustments — (2,043) — (2,043) Effect of net foreign currency exchange rate changes 80 1,231 6 1,317 Balance as of December 31, 2019 113,426 80,873 744 195,043 test IO purchase accounting adjustment 863 (1,089) — (226) Other 2019 acquisitions purchase accounting adjustments 219 259 21 499 2020 Acquisitions (Note 2) 6,042 6,903 — 12,945 Effect of net foreign currency exchange rate changes 582 3,160 (47) 3,695 Balance as of December 31, 2020 $ 121,132 $ 90,106 $ 718 $ 211,956
Components of Intangible Assets	Intangible assets other than goodwill as of December 31, 2020 and 2019 were as follows: As of December 31, 2020 Weighted average life at acquisition (in years) Gross carrying amount Accumulated amortization Net Customer relationships 9 $ 94,169 $ (49,415) $ 44,754 Software 6 6,309 (1,633) 4,676 Trade names 5 6,495 (5,273) 1,222 Contract royalties 8 1,900 (673) 1,227 Assembled workforce 3 157 (61) 96 Total $ 109,030 $ (57,055) $ 51,975 As of December 31, 2019 Weighted average life at acquisition (in years) Gross carrying amount Accumulated amortization Net Customer relationships 9 $ 87,489 $ (38,526) $ 48,963 Software 6 4,472 (486) 3,986 Trade names 5 6,439 (4,753) 1,686 Contract royalties 8 1,900 (435) 1,465 Assembled workforce 3 158 — 158 Total $ 100,458 $ (44,200) $ 56,258
Intangible Assets Amortization Expense Recognized	The following table presents amortization expense recognized for the periods indicated: For the Years Ended December 31, 2020 2019 2018 Customer relationships $ 10,478 $ 8,743 $ 7,637 Software 1,068 486 — Trade names 495 447 266 Contract royalties 238 238 198 Assembled workforce 61 — — Favorable lease — — 410 Total $ 12,340 $ 9,914 $ 8,511
Estimated Amortization Expense	Based on the carrying value of the Company’s existing intangible assets as of December 31, 2020, the estimated amortization expense for the future years is as follows: Year ending December 31, Amount 2021 $ 12,585 2022 12,426 2023 11,115 2024 8,586 2025 5,543 Thereafter 1,720 Total $ 51,975

FAIR VALUE MEASUREMENTS (Tables

FAIR VALUE MEASUREMENTS (Tables)	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis	The following table shows the fair values of the Company’s financial assets and liabilities measured at fair value on a recurring basis as of December 31, 2020: As of December 31, 2020 Balance Level 1 Level 2 Level 3 Foreign exchange derivative assets $ 4,955 $ — $ 4,955 $ — Total assets measured at fair value on a recurring basis $ 4,955 $ — $ 4,955 $ — Foreign exchange derivative liabilities $ 243 $ — $ 243 $ — Contingent consideration 7,470 — — 7,470 Total liabilities measured at fair value on a recurring basis $ 7,713 $ — $ 243 $ 7,470 The following table shows the fair values of the Company’s financial assets and liabilities measured at fair value on a recurring basis as of December 31, 2019. As of December 31, 2019 Balance Level 1 Level 2 Level 3 Foreign exchange derivative assets $ 1,910 $ — $ 1,910 $ — Total assets measured at fair value on a recurring basis $ 1,910 $ — $ 1,910 $ — Foreign exchange derivative liabilities $ 243 $ — $ 243 $ — Contingent consideration 10,495 — — 10,495 Total liabilities measured at fair value on a recurring basis $ 10,738 $ — $ 243 $ 10,495
Reconciliation of Acquisition-Related Contractual Contingent Consideration Using Significant Unobservable Inputs	A reconciliation of the beginning and ending balances of Level 3 acquisition-related contractual contingent consideration using significant unobservable inputs for the years ended December 31, 2018, December 31, 2019 and December 31, 2020 are as follows: Amount Contractual contingent liabilities as of January 1, 2018 $ — Acquisition date fair value of contingent consideration — Continuum acquisition (Note 2) 2,400 Acquisition date fair value of contingent consideration — Think acquisition (Note 2) 5,990 Changes in fair value of contingent consideration included in Interest and other income, net (900) Effect of net foreign currency exchange rate changes (22) Contractual contingent liabilities as of December 31, 2018 $ 7,468 Payment of contingent consideration for previously acquired businesses (1,104) Acquisition date fair value of contingent consideration — Other 2019 Acquisitions (Note 2) 2,100 Changes in fair value of contingent consideration included in Interest and other income, net 1,776 Effect of net foreign currency exchange rate changes 255 Contractual contingent liabilities as of December 31, 2019 $ 10,495 Payment of contingent consideration for previously acquired businesses (9,619) Acquisition date fair value of contingent consideration — 2020 Acquisitions (Note 2) 5,292 Changes in fair value of contingent consideration included in Interest and other income, net 1,827 Effect of net foreign currency exchange rate changes (525) Contractual contingent consideration liabilities as of December 31, 2020 $ 7,470
Estimated Fair Values of Financial Assets and Liabilities Not Measured at Fair Value on a Recurring Basis	The following tables present the estimated fair values of the Company’s financial assets and liabilities not measured at fair value on a recurring basis as of the dates indicated: Fair Value Hierarchy Balance Estimated Fair Value Level 1 Level 2 Level 3 December 31, 2020 Financial Assets: Cash equivalents: Money market funds $ 153,783 $ 153,783 $ 153,783 $ — $ — Total cash equivalents $ 153,783 $ 153,783 $ 153,783 $ — $ — Restricted cash $ 1,390 $ 1,390 $ 1,390 $ — $ — Time deposits included in Short-term investments $ 60,007 $ 60,007 $ — $ 60,007 $ — Employee loans $ 794 $ 794 $ — $ — $ 794 Financial Liabilities: Borrowings under 2017 Credit Facility $ 25,007 $ 25,007 $ — $ 25,007 $ — Fair Value Hierarchy Balance Estimated Fair Value Level 1 Level 2 Level 3 December 31, 2019 Financial Assets: Cash equivalents: Money market funds $ 407,817 $ 407,817 $ 407,817 $ — $ — Time deposits 10,002 10,002 — 10,002 — Total cash equivalents $ 417,819 $ 417,819 $ 407,817 $ 10,002 $ — Restricted cash $ 1,136 $ 1,136 $ 1,136 $ — $ — Employee loans $ 2,434 $ 2,434 $ — $ — $ 2,434 Financial Liabilities: Borrowings under 2017 Credit Facility $ 25,017 $ 25,017 $ — $ 25,017 $ —

DERIVATIVE FINANCIAL INSTRUME_2

DERIVATIVE FINANCIAL INSTRUMENTS (Tables)	12 Months Ended
	Dec. 31, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Fair Value of Derivative Instruments	The fair value of foreign currency derivative instruments on the Company’s consolidated balance sheets as of December 31, 2020 and December 31, 2019 were as follows: As of December 31, 2020 As of December 31, 2019 Balance Sheet Classification Asset Derivatives Liability Derivatives Asset Derivatives Liability Derivatives Foreign exchange forward contracts - Designated as hedging instruments Prepaid and other current assets $ 4,955 $ 1,910 Accrued expenses and other current liabilities $ 243 $ 243

PROPERTY AND EQUIPMENT, NET (Ta

PROPERTY AND EQUIPMENT, NET (Tables)	12 Months Ended
	Dec. 31, 2020
Property, Plant and Equipment [Abstract]
Components of Property and Equipment, Net	Property and equipment, net consisted of the following: Weighted Average Useful Life As of December 31, 2020 As of December 31, 2019 Computer hardware 3 $ 117,333 $ 96,286 Buildings 46 52,007 51,300 Leasehold improvements 7 39,675 30,634 Purchased computer software 3 31,993 32,115 Furniture, fixture and other equipment 7 31,859 28,193 Office equipment 7 20,971 18,901 Land improvements 18 2,137 2,137 Land n/a 1,339 — 297,314 259,566 Less accumulated depreciation and amortization (127,781) (94,307) Total $ 169,533 $ 165,259

ACCRUED EXPENSES AND OTHER CU_2

ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES (Tables)	12 Months Ended
	Dec. 31, 2020
Payables and Accruals [Abstract]
Components of Accrued Expenses and Other Current Liabilities	Accrued expenses and other current liabilities consisted of the following: As of December 31, 2020 As of December 31, 2019 Value added taxes payable $ 34,522 $ 24,016 Deferred revenue 17,383 9,132 Contingent consideration, current (Note 4) 1,125 10,057 Other current liabilities and accrued expenses 26,660 39,271 Total $ 79,690 $ 82,476

LEASES (Tables)

LEASES (Tables)	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Components of Lease Expenses	During the years ended December 31, 2020 and 2019, the components of lease expense were as follows: Income Statement Classification Year Ended December 31, 2020 Year Ended December 31, 2019 Operating lease cost Selling, general and administrative expenses $ 73,740 $ 62,740 Variable lease cost Selling, general and administrative expenses 6,461 8,730 Short-term lease cost Selling, general and administrative expenses 1,169 3,870 Total lease cost $ 81,370 $ 75,340
Supplemental Cash Flow Information	Supplemental cash flow information related to leases was as follows: Year Ended December 31, 2020 Year Ended December 31, 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows used for operating leases $ 70,012 $ 59,952 Right-of-use assets obtained in exchange for lease obligations: Operating leases $ 50,949 $ 107,822 Non-cash net increase due to lease modifications: Operating lease right-of-use assets $ 7,876 $ 10,124 Operating lease liabilities $ 7,861 $ 10,192
Weighted Average Remaining Lease Term and Discount Rate	Weighted average remaining lease terms and discount rates as of December 31, 2020, were as follows: As of December 31, 2020 As of December 31, 2019 Weighted average remaining lease term, in years: Operating leases 5.9 6.1 Weighted average discount rate: Operating leases 2.9 % 3.6 %
Maturity of Operating Lease Liabilities	As of December 31, 2020, operating lease liabilities will mature as follows: Year ending December 31, Lease Payments 2021 $ 66,585 2022 50,147 2023 37,268 2024 32,400 2025 22,859 Thereafter 52,531 Total lease payments 261,790 Less: imputed interest (20,427) Total $ 241,363

LONG-TERM DEBT (Tables)

LONG-TERM DEBT (Tables)	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Outstanding Debt And Borrowing Capacity under 2017 Credit Facility	The following table presents the outstanding debt and borrowing capacity of the Company under the 2017 Credit Facility: As of December 31, 2020 As of December 31, 2019 Outstanding debt $ 25,000 $ 25,000 Interest rate 1.2 % 2.8 % Irrevocable standby letters of credit $ — $ 303 Available borrowing capacity $ 275,000 $ 274,697 Current maximum borrowing capacity $ 300,000 $ 300,000

REVENUES (Tables)

REVENUES (Tables)	12 Months Ended
	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenues	The following tables show the disaggregation of the Company’s revenues by major customer location, including a reconciliation of the disaggregated revenues with the Company’s reportable segments (Note 16 “Segment Information”) for the years ended December 31, 2020, 2019 and 2018: Year Ended December 31, 2020 Reportable Segments North America Europe Russia Consolidated Revenues Customer Locations North America $ 1,546,093 $ 45,553 $ 3,490 $ 1,595,136 Europe 45,733 834,033 76 879,842 CIS 7,817 98 106,787 114,702 APAC 2,177 67,621 — 69,798 Revenues $ 1,601,820 $ 947,305 $ 110,353 $ 2,659,478 Year Ended December 31, 2019 Reportable Segments North America Europe Russia Consolidated Revenues Customer Locations North America $ 1,344,040 $ 45,859 $ 116 $ 1,390,015 Europe 27,042 719,548 276 746,866 CIS 8,583 143 91,745 100,471 APAC 1,279 55,167 — 56,446 Revenues $ 1,380,944 $ 820,717 $ 92,137 $ 2,293,798 Year Ended December 31, 2018 Reportable Segments North America Europe Russia Consolidated Revenues Customer Locations North America $ 1,046,232 $ 52,860 $ 75 $ 1,099,167 Europe 16,679 595,741 52 612,472 CIS 8,437 336 72,930 81,703 APAC 5,631 43,848 91 49,570 Revenues $ 1,076,979 $ 692,785 $ 73,148 $ 1,842,912 The following tables show the disaggregation of the Company’s revenues by industry vertical, including a reconciliation of the disaggregated revenues with the Company’s reportable segments (Note 16 “Segment Information”) for the years ended December 31, 2020, 2019 and 2018: Year Ended December 31, 2020 Reportable Segments North America Europe Russia Consolidated Revenues Industry Verticals Business Information & Media $ 334,063 $ 224,922 $ 1,695 $ 560,680 Financial Services 199,594 278,355 77,286 555,235 Software & Hi-Tech 419,895 73,288 3,630 496,813 Travel & Consumer 221,977 220,448 16,364 458,789 Life Sciences & Healthcare 260,518 35,347 448 296,313 Emerging Verticals 165,773 114,945 10,930 291,648 Revenues $ 1,601,820 $ 947,305 $ 110,353 $ 2,659,478 Year Ended December 31, 2019 Reportable Segments North America Europe Russia Consolidated Revenues Industry Verticals Business Information & Media $ 262,448 $ 157,844 $ 631 $ 420,923 Financial Services 184,469 244,284 72,119 500,872 Software & Hi-Tech 354,023 77,377 1,998 433,398 Travel & Consumer 198,264 229,523 11,571 439,358 Life Sciences & Healthcare 224,925 23,444 83 248,452 Emerging Verticals 156,815 88,245 5,735 250,795 Revenues $ 1,380,944 $ 820,717 $ 92,137 $ 2,293,798 Year Ended December 31, 2018 Reportable Segments North America Europe Russia Consolidated Revenues Industry Verticals Business Information & Media $ 251,081 $ 72,898 $ 54 $ 324,033 Financial Services $ 112,444 $ 252,196 $ 59,337 $ 423,977 Software & Hi-Tech 269,067 79,121 2,627 350,815 Travel & Consumer 177,910 208,266 7,467 393,643 Life Sciences & Healthcare 151,418 20,272 13 171,703 Emerging Verticals 115,059 60,032 3,650 178,741 Revenues $ 1,076,979 $ 692,785 $ 73,148 $ 1,842,912 The Company derives revenues from a variety of customized and integrated service arrangements. Fees for these contracts may be in the form of time-and-materials or fixed-price arrangements. The following tables show the disaggregation of the Company’s revenues by contract type, including a reconciliation of the disaggregated revenues with the Company’s reportable segments (Note 16 “Segment Information”) for the years ended December 31, 2020, 2019 and 2018: Year Ended December 31, 2020 Reportable Segments North America Europe Russia Consolidated Revenues Contract Types Time-and-material $ 1,440,635 $ 790,203 $ 60,166 $ 2,291,004 Fixed-price 151,769 151,718 48,525 352,012 Licensing 8,027 1,526 1,586 11,139 Other revenues 1,389 3,858 76 5,323 Revenues $ 1,601,820 $ 947,305 $ 110,353 $ 2,659,478 Year Ended December 31, 2019 Reportable Segments North America Europe Russia Consolidated Revenues Contract Types Time-and-material $ 1,247,979 $ 688,605 $ 54,069 $ 1,990,653 Fixed-price 127,926 128,977 37,747 294,650 Licensing 3,626 1,230 225 5,081 Other revenues 1,413 1,905 96 3,414 Revenues $ 1,380,944 $ 820,717 $ 92,137 $ 2,293,798 Year Ended December 31, 2018 Reportable Segments North America Europe Russia Consolidated Revenues Contract Types Time-and-material $ 983,436 $ 628,707 $ 40,754 $ 1,652,897 Fixed-price 89,831 62,078 32,342 184,251 Licensing 2,748 1,332 17 4,097 Other revenues 964 668 35 1,667 Revenues $ 1,076,979 $ 692,785 $ 73,148 $ 1,842,912 Timing of Revenue Recognition The following tables show the timing of revenue recognition: Year Ended December 31, 2020 Reportable Segments North America Europe Russia Consolidated Revenues Timing of Revenue Recognition Transferred over time $ 1,595,786 $ 946,379 $ 108,826 $ 2,650,991 Transferred at a point of time 6,034 926 1,527 8,487 Revenues $ 1,601,820 $ 947,305 $ 110,353 $ 2,659,478 Year Ended December 31, 2019 Reportable Segments North America Europe Russia Consolidated Revenues Timing of Revenue Recognition Transferred over time $ 1,379,256 $ 819,913 $ 92,076 $ 2,291,245 Transferred at a point of time 1,688 804 61 2,553 Revenues $ 1,380,944 $ 820,717 $ 92,137 $ 2,293,798
Timing of Revenue Recognition	The following table includes the estimated revenues expected to be recognized in the future related to performance obligations that are partially or fully unsatisfied as of December 31, 2020. The Company applies a practical expedient and does not disclose the value of unsatisfied performance obligations for contracts that (i) have an original expected duration of one year or less and (ii) contracts for which it recognizes revenues at the amount to which it has the right to invoice for services provided: Less than 1 year 1 Year 2 Years 3 Years Total Contract Type Fixed-price $ 7,885 $ 103 $ — $ — $ 7,988
Classification of Contract Assets and Liabilities	The following table provides information on the classification of contract assets and liabilities in the consolidated balance sheets: As of December 31, 2020 As of December 31, 2019 Contract assets included in Trade receivables and contract assets $ 7,700 $ 14,320 Contract liabilities included in Accrued expenses and other current liabilities $ 17,383 $ 9,132 Contract liabilities included in Other noncurrent liabilities $ 94 $ 5

STOCK-BASED COMPENSATION (Table

STOCK-BASED COMPENSATION (Tables)	12 Months Ended
	Dec. 31, 2020
Share-based Payment Arrangement [Abstract]
Costs Related to Stock Compensation Plans	The following costs related to the Company’s stock compensation plans were included in the consolidated statements of income and comprehensive income: For the Years Ended December 31, 2020 2019 2018 Cost of revenues (exclusive of depreciation and amortization) $ 32,785 $ 37,580 $ 27,245 Selling, general and administrative expenses 42,453 34,456 31,943 Total $ 75,238 $ 72,036 $ 59,188
Stock Option Activity	Stock option activity under the Company’s plans is set forth below: Number of Weighted Average Aggregate Weighted Average Options outstanding as of January 1, 2018 4,902 $ 40.91 $ 326,064 Options granted 160 $ 112.81 Options exercised (945) $ 36.69 Options forfeited/cancelled (33) $ 63.28 Options expired (1) $ 25.72 Options outstanding as of December 31, 2018 4,083 $ 44.54 $ 291,846 Options granted 132 $ 169.13 Options modified 18 $ 163.55 Options exercised (899) $ 41.21 Options forfeited/cancelled (11) $ 97.83 Options outstanding as of December 31, 2019 3,323 $ 50.85 $ 536,015 Options granted 158 $ 187.76 Options modified — $ — Options exercised (700) $ 37.79 Options forfeited/cancelled (9) $ 119.30 Options outstanding as of December 31, 2020 2,772 $ 61.71 $ 822,152 4.3 Options vested and exercisable as of December 31, 2020 2,388 $ 46.99 $ 743,582 3.7 Options expected to vest as of December 31, 2020 362 $ 152.22 $ 74,548 8.2
Black-Scholes Option Valuation Model Assumptions	The fair value of each option award is estimated on the date of grant using the Black-Scholes option valuation model. The model incorporated the following weighted-average assumptions: For the Years Ended December 31, 2020 2019 2018 Expected volatility 36.9 % 33.5 % 33.8 % Expected term (in years) 6.25 6.25 6.25 Risk-free interest rate 0.5 % 2.3 % 2.7 % Expected dividends — % — % — %
Service-Based Awards Activity	The table below summarizes activity related to the Company’s equity-classified and liability-classified service-based awards for the years ended December 31, 2020, 2019 and 2018: Equity-Classified Equity-Classified Equity-Settled Restricted Stock Units Liability-Classified Cash-Settled Restricted Stock Units Number of Weighted Average Grant Date Number of Weighted Average Grant Date Number of Weighted Average Grant Date Unvested service-based awards outstanding as of January 1, 2018 2 $ 54.37 688 $ 71.60 315 $ 72.50 Awards granted — $ — 381 $ 115.84 85 $ 112.65 Awards modified — $ — (3) $ 80.27 3 $ 120.18 Awards vested (1) $ 47.76 (218) $ 70.10 (92) $ 72.69 Awards forfeited/cancelled — $ — (50) $ 86.97 (8) $ 81.40 Unvested service-based awards outstanding as of December 31, 2018 1 $ 63.10 798 $ 92.13 303 $ 83.99 Awards granted 9 $ 167.18 284 $ 170.29 56 $ 170.13 Awards modified — $ — 7 $ 170.74 1 $ 168.36 Awards vested — $ — (287) $ 87.79 (111) $ 80.51 Awards forfeited/cancelled — $ — (43) $ 114.45 (7) $ 94.77 Unvested service-based awards outstanding as of December 31, 2019 10 $ 162.96 759 $ 122.48 242 $ 105.40 Awards granted — $ — 294 $ 204.57 60 $ 181.77 Awards modified — $ — (1) $ 122.55 — $ — Awards vested (1) $ 63.10 (317) $ 108.87 (122) $ 91.39 Awards forfeited/cancelled — $ — (49) $ 148.11 (5) $ 113.94 Unvested service-based awards outstanding as of December 31, 2020 9 $ 167.18 686 $ 162.15 175 $ 141.16
Fair Value of Service-Based Awards Vested	The fair value of vested service-based awards (measured at the vesting date) for the years ended December 31, 2020, 2019 and 2018 was as follows: For the Years Ended December 31, 2020 2019 2018 Equity-classified equity-settled Restricted stock $ 101 $ 73 $ 142 Restricted stock units 60,042 48,111 24,987 Liability-classified cash-settled Restricted stock units 22,014 18,449 10,349 Total fair value of vested service-based awards $ 82,157 $ 66,633 $ 35,478
Performance-Based Awards Activity	The table below summarizes activity related to the Company’s performance-based awards for the years ended December 31, 2020, 2019 and 2018: Equity-Classified Equity-Classified Number of Weighted Average Grant Date Number of Weighted Average Grant Date Unvested performance-based awards outstanding as of January 1, 2018 — $ — — $ — Awards granted — $ — 45 $ 121.75 Awards vested — $ — (8) $ 121.75 Awards forfeited/cancelled — $ — (7) $ 121.75 Unvested performance-based awards outstanding as of December 31, 2018 — $ — 30 $ 121.75 Awards granted 9 $ 165.87 — $ — Awards modified — $ — (30) $ 121.75 Unvested performance-based awards outstanding as of December 31, 2019 9 $ 165.87 — $ — Awards granted — $ — 31 $ 210.44 Awards vested — $ — (10) $ 177.81 Unvested performance-based awards outstanding as of December 31, 2020 9 $ 165.87 21 $ 227.16
Fair Value of Performance-Based Awards Vested	The fair value of vested performance-based awards (measured at the vesting date) for the years ended December 31, 2020, 2019 and 2018 was as follows: For the Years Ended December 31, 2020 2019 2018 Equity-classified equity-settled Restricted stock units $ 3,282 — $ 1,046 Total fair value of vested performance-based awards $ 3,282 $ — $ 1,046

INCOME TAXES (Tables)

INCOME TAXES (Tables)	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Income Before Provision of Income Taxes	Income before provision for income taxes based on geographic location is disclosed in the table below: For the Years Ended December 31, 2020 2019 2018 Income before provision for income taxes: United States $ 100,411 $ 65,370 $ 44,527 Foreign 278,068 234,156 205,246 Total $ 378,479 $ 299,526 $ 249,773
Provision for Income Taxes	The provision for income taxes consists of the following: For the Years Ended December 31, 2020 2019 2018 Current Federal $ 19,249 $ 16,943 $ 10,814 State 7,022 3,610 4,123 Foreign 45,042 25,680 42,580 Deferred Federal (16,235) (9,425) (37,785) State (1,682) (358) (3,548) Foreign (2,077) 2,019 (6,667) Total $ 51,319 $ 38,469 $ 9,517
Effective Tax Rate Reconciliation	The reconciliation of the provision for income taxes at the federal statutory income tax rate to the Company’s effective income tax rate is as follows: For the Years Ended December 31, 2020 2019 2018 Provision for income taxes at federal statutory rate $ 79,481 $ 62,898 $ 52,452 Increase/(decrease) in taxes resulting from: Impact from U.S. Tax Act — — (4,009) Entity classification election deferred tax asset impact — — (25,962) GILTI and BEAT U.S. taxes 191 (926) 1,526 Excess tax benefits relating to stock-based compensation (36,646) (28,385) (17,370) Subsidiary withholding tax liability and related foreign tax credit — — (4,850) Foreign tax expense and tax rate differential (387) (1,402) (88) Effect of permanent differences 3,507 3,264 2,724 State taxes, net of federal benefit 5,323 2,971 3,452 Stock-based compensation expense 44 571 652 Other (194) (522) 990 Provision for income taxes $ 51,319 $ 38,469 $ 9,517
Significant Components of Deferred Tax Assets and Liabilities	Significant components of the Company’s deferred tax assets and liabilities are as follows: As of December 31, 2020 As of December 31, 2019 Deferred tax assets: Property and equipment $ 8,164 $ 5,329 Intangible assets 827 574 Accrued expenses 50,639 41,457 Net operating loss carryforward 6,089 5,168 Deferred revenue 9,796 3,510 Stock-based compensation 30,112 29,596 Operating lease liabilities 51,519 7,438 Foreign tax credit 2,168 3,491 Foreign currency exchange 4,890 2,499 Other assets 1,252 1,533 Deferred tax assets $ 165,456 $ 100,595 Less: valuation allowance (5,485) (3,877) Total deferred tax assets $ 159,971 $ 96,718 Deferred tax liabilities: Property and equipment $ 3,818 $ 4,981 Intangible assets 12,018 11,364 Operating lease right-of-use assets 50,149 6,900 Accrued revenue and expenses 991 2,176 U.S. taxation of foreign subsidiaries 1,608 — Foreign currency exchange 1,153 375 Other liabilities 1,095 437 Total deferred tax liabilities $ 70,832 $ 26,233 Net deferred tax assets $ 89,139 $ 70,485

EARNINGS PER SHARE (Tables)

EARNINGS PER SHARE (Tables)	12 Months Ended
	Dec. 31, 2020
Earnings Per Share [Abstract]
Computation of Basic and Diluted Earnings Per Share	The following table sets forth the computation of basic and diluted earnings per share of common stock as follows: For the Years Ended December 31, 2020 2019 2018 Numerator for basic and diluted earnings per share: Net income $ 327,160 $ 261,057 $ 240,256 Numerator for basic and diluted earnings per share $ 327,160 $ 261,057 $ 240,256 Denominator: Weighted average common shares for basic earnings per share 55,727 54,719 53,623 Net effect of dilutive stock options, restricted stock units and restricted stock awards 2,719 2,949 3,050 Weighted average common shares for diluted earnings per share 58,446 57,668 56,673 Net Income per share: Basic $ 5.87 $ 4.77 $ 4.48 Diluted $ 5.60 $ 4.53 $ 4.24

SEGMENT INFORMATION (Tables)

SEGMENT INFORMATION (Tables)	12 Months Ended
	Dec. 31, 2020
Segment Reporting [Abstract]
Revenues from External Customers and Operating Profit Before Unallocated Expenses	Revenues from external customers and operating profit, before unallocated expenses, by reportable segments were as follows: For the years ended December 31, 2020 2019 2018 Segment revenues: North America $ 1,601,820 $ 1,380,944 $ 1,076,979 Europe 947,305 820,717 692,785 Russia 110,353 92,137 73,148 Total revenues $ 2,659,478 $ 2,293,798 $ 1,842,912 Segment operating profit: North America $ 345,196 $ 293,757 $ 221,846 Europe 152,902 114,863 115,876 Russia 5,811 17,347 11,377 Total segment operating profit $ 503,909 $ 425,967 $ 349,099
Reconciliation of Segment Operating Profit to Consolidated Income Before Provision for Income Taxes	Reconciliation of segment operating profit to consolidated income before provision for income taxes is presented below: For the Years Ended December 31, 2020 2019 2018 Total segment operating profit: $ 503,909 $ 425,967 $ 349,099 Unallocated costs: Stock-based compensation expense (75,238) (72,036) (59,188) Amortization of purchased intangibles (12,340) (9,914) (8,101) Other acquisition-related expenses (1,868) (3,774) (916) Other unallocated costs (35,139) (37,393) (35,130) Income from operations 379,324 302,850 245,764 Interest and other income, net 3,822 8,725 3,522 Foreign exchange (loss)/gain (4,667) (12,049) 487 Income before provision for income taxes $ 378,479 $ 299,526 $ 249,773
Physical Locations and Values of Long-Lived Assets	Physical locations and values of the Company’s long-lived assets are presented below: As of December 31, 2020 As of December 31, 2019 As of December 31, 2018 Belarus $ 73,988 $ 75,984 $ 50,085 Ukraine 30,980 24,652 8,433 United States 15,718 15,637 13,101 Russia 15,036 17,980 9,902 India 7,079 7,443 7,019 Poland 5,434 5,029 2,637 Hungary 5,365 5,201 3,168 Spain 2,799 1,106 875 China 2,722 3,036 2,651 Mexico 2,419 2,353 812 Other 7,993 6,838 3,963 Total $ 169,533 $ 165,259 $ 102,646
Revenues by Customer Location	The table below presents the Company’s revenues by customer location for the years ended December 31, 2020, 2019 and 2018: For the Years Ended December 31, 2020 2019 2018 United States $ 1,523,731 $ 1,321,662 $ 1,029,327 United Kingdom 331,217 290,039 200,918 Switzerland 203,391 152,710 144,398 Netherlands 114,678 88,488 70,274 Russia 104,846 89,941 71,181 Germany 84,902 82,441 80,787 Canada 68,416 68,304 69,836 Other locations 228,297 200,213 176,191 Revenues $ 2,659,478 $ 2,293,798 $ 1,842,912

ACCUMULATED OTHER COMPREHENSI_2

ACCUMULATED OTHER COMPREHENSIVE LOSS (Tables)	12 Months Ended
	Dec. 31, 2020
Equity [Abstract]
Components of Accumulated Other Comprehensive Loss	The following table summarizes the changes in the accumulated balances for each component of accumulated other comprehensive loss: For the Years Ended December 31, 2020 2019 2018 Foreign currency translation Beginning balance $ (32,666) $ (38,961) $ (17,623) Foreign currency translation 5,802 7,912 (25,097) Income tax (expense)/benefit (1,304) (1,617) 3,759 Foreign currency translation, net of tax 4,498 6,295 (21,338) Ending balance $ (28,168) $ (32,666) $ (38,961) Cash flow hedging instruments Beginning balance $ 1,292 $ (2,553) $ — Unrealized gain in fair value 8,076 2,933 867 Net (loss)/gain reclassified into Cost of revenues (exclusive of depreciation and amortization) (5,031) 2,028 (4,161) Income tax (expense)/benefit (695) (1,116) 741 Cash flow hedging instruments, net of tax 2,350 3,845 (2,553) Ending balance (1) $ 3,642 $ 1,292 $ (2,553) Defined benefit plans Beginning balance $ — $ — $ — Actuarial losses (1,275) — — Income tax benefit 289 — — Defined benefit plans, net of tax (986) — — Ending balance $ (986) $ — $ — Accumulated other comprehensive loss $ (25,512) $ (31,374) $ (41,514)

QUARTERLY FINANCIAL DATA (UNA_2

QUARTERLY FINANCIAL DATA (UNAUDITED) (Tables)	12 Months Ended
	Dec. 31, 2020
Quarterly Financial Information Disclosure [Abstract]
Schedule of Quarterly Financial Information	Summarized quarterly results for the years ended December 31, 2020 and 2019 were as follows: Three Months Ended 2020 March 31 June 30 September 30 December 31 Full Year Revenues $ 651,359 $ 632,383 $ 652,243 $ 723,493 $ 2,659,478 Operating expenses: Cost of revenues (exclusive of depreciation and amortization) 423,802 419,540 423,388 465,792 1,732,522 Selling, general and administrative expenses 125,108 114,191 116,530 128,929 484,758 Depreciation and amortization expense 14,940 15,226 15,929 16,779 62,874 Income from operations 87,509 83,426 96,396 111,993 379,324 Interest and other income/(expense), net 2,386 1,817 1,672 (2,053) 3,822 Foreign exchange gain/(loss) 6,524 (9,167) 5,896 (7,920) (4,667) Income before provision for income taxes 96,419 76,076 103,964 102,020 378,479 Provision for income taxes 10,854 9,452 14,532 16,481 51,319 Net income $ 85,565 $ 66,624 $ 89,432 $ 85,539 $ 327,160 Comprehensive income $ 47,678 $ 85,512 $ 89,133 $ 110,699 $ 333,022 Basic net income per share (1) $ 1.55 $ 1.20 $ 1.60 $ 1.53 $ 5.87 Diluted net income per share (1) $ 1.47 $ 1.14 $ 1.53 $ 1.46 $ 5.60 (1) Earnings per share amounts for each quarter may not necessarily total to the yearly earnings per share due to the weighting of shares outstanding on a quarterly and year to date basis. Three Months Ended 2019 March 31 June 30 September 30 December 31 Full Year Revenues $ 521,333 $ 551,587 $ 588,103 $ 632,775 $ 2,293,798 Operating expenses: Cost of revenues (exclusive of depreciation and amortization) 344,689 355,915 377,525 410,069 1,488,198 Selling, general and administrative expenses 101,786 111,762 118,886 124,999 457,433 Depreciation and amortization expense 10,200 11,028 11,127 12,962 45,317 Income from operations 64,658 72,882 80,565 84,745 302,850 Interest and other income, net 3,076 1,190 2,509 1,950 8,725 Foreign exchange loss (3,484) (3,562) (3,105) (1,898) (12,049) Income before provision for income taxes 64,250 70,510 79,969 84,797 299,526 Provision for income taxes 3,496 11,733 12,967 10,273 38,469 Net income $ 60,754 $ 58,777 $ 67,002 $ 74,524 $ 261,057 Comprehensive income $ 66,797 $ 62,934 $ 54,725 $ 86,741 $ 271,197 Basic net income per share (1) $ 1.12 $ 1.07 $ 1.22 $ 1.35 $ 4.77 Diluted net income per share (1) $ 1.06 $ 1.02 $ 1.16 $ 1.29 $ 4.53 (1) Earnings per share amounts for each quarter may not necessarily total to the yearly earnings per share due to the weighting of shares outstanding on a quarterly and year to date basis.

VALUATION AND QUALIFYING ACCO_2

VALUATION AND QUALIFYING ACCOUNTS (Tables)	12 Months Ended
	Dec. 31, 2020
SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract]
Valuation and Qualifying Accounts	Balance at Additions Deductions/ Balance at End of Year Year Ended December 31, 2020 Allowance for doubtful accounts for trade receivables and contract assets $ 3,210 3,282 (1,606) $ 4,886 Valuation allowance on deferred tax assets $ 3,877 1,608 — $ 5,485 Year Ended December 31, 2019 Allowance for doubtful accounts for trade receivables and contract assets $ 1,557 2,072 (419) $ 3,210 Valuation allowance on deferred tax assets $ 3,189 688 — $ 3,877 Year Ended December 31, 2018 Allowance for doubtful accounts for trade receivables and contract assets $ 1,186 2,722 (2,351) $ 1,557 Valuation allowance on deferred tax assets $ 924 2,265 — $ 3,189

BUSINESS AND SUMMARY OF SIGNI_3

BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Property and Equipment) (Details)	12 Months Ended
	Dec. 31, 2020
Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)	2 years
Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)	50 years

BUSINESS AND SUMMARY OF SIGNI_4

BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Goodwill and Other Indefinite-Lived Intangible Assets) (Details) $ in Thousands	Dec. 31, 2020USD ($)
Accounting Policies [Abstract]
Indefinite-lived intangible assets other than goodwill	$ 0

BUSINESS AND SUMMARY OF SIGNI_5

BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Effect of Adoption of Topic 606) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Statement
Revenues	$ 723,493	$ 652,243	$ 632,383	$ 651,359	$ 632,775	$ 588,103	$ 551,587	$ 521,333	$ 2,659,478	$ 2,293,798	$ 1,842,912
Income from operations	111,993	96,396	83,426	87,509	84,745	80,565	72,882	64,658	379,324	302,850	245,764
Provision for income taxes	16,481	14,532	9,452	10,854	10,273	12,967	11,733	3,496	51,319	38,469	9,517
Net income	$ 85,539	$ 89,432	$ 66,624	$ 85,565	$ 74,524	$ 67,002	$ 58,777	$ 60,754	$ 327,160	$ 261,057	240,256
Balance Under Revenue Guidance in Effect Before Topic 606
Income Statement
Revenues											1,843,159
Income from operations											246,011
Provision for income taxes											9,572
Net income											240,448
Topic 606 | Adjustments
Income Statement
Revenues											(247)
Income from operations											(247)
Provision for income taxes											(55)
Net income											$ (192)

BUSINESS AND SUMMARY OF SIGNI_6

BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Risks and Uncertainties) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Concentration Risk [Line Items]
Total cash	$ 1,323,533	$ 937,688	$ 771,711	$ 582,855
Belarus, Russia, Ukraine, Kazakhstan, Armenia, Georgia and Uzbekistan | Geographic concentration risk | Total cash
Concentration Risk [Line Items]
Total cash	146,200
Belarus | Geographic concentration risk | Total cash
Concentration Risk [Line Items]
Total cash	$ 52,900

BUSINESS AND SUMMARY OF SIGNI_7

BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Lease) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Jan. 01, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
RoU Assets for operating leases	$ 228,672	$ 238,991
Operating lease liabilities	$ 241,363
Topic 842
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
RoU Assets for operating leases			$ 177,600
Operating lease liabilities			$ 173,900

ACQUISITIONS (Narrative) (Detai

ACQUISITIONS (Narrative) (Details) $ in Thousands	Apr. 30, 2019USD ($)	Nov. 01, 2018USD ($)	Mar. 15, 2018USD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Business Acquisition [Line Items]
Acquisition-date fair value of contingent consideration issued for acquisition of businesses				$ 7,119	$ 3,876	$ 8,390
Continuum
Business Acquisition [Line Items]
Acquisition date			Mar. 15, 2018
Cash consideration			$ 52,500
Acquisition-date fair value of contingent consideration issued for acquisition of businesses			2,400
Maximum amount of earnout payable			$ 3,100
Estimated future operating results, period			12 months
Continuum | Design Consultant
Business Acquisition [Line Items]
Numbers of professionals acquired			125
Think
Business Acquisition [Line Items]
Acquisition date		Nov. 1, 2018
Cash consideration		$ 26,300
Acquisition-date fair value of contingent consideration issued for acquisition of businesses		6,000
Maximum amount of earnout payable		$ 8,200
Estimated future operating results, period		12 months
test IO
Business Acquisition [Line Items]
Acquisition date	Apr. 30, 2019
Cash consideration	$ 17,300
Equity interest acquired	100.00%
Other 2019 Acquisitions
Business Acquisition [Line Items]
Cash consideration					24,800
Maximum amount of earnout payable					$ 3,000
Number of completed acquisitions					4
Other 2019 Acquisitions | Minimum
Business Acquisition [Line Items]
Estimated future operating results, period					12 months
Other 2019 Acquisitions | Maximum
Business Acquisition [Line Items]
Estimated future operating results, period					24 months
2020 Acquisitions
Business Acquisition [Line Items]
Aggregate purchase price including contingent consideration at fair value at acquisition date				22,500
Acquisition-date fair value of contingent consideration issued for acquisition of businesses				5,300
Maximum amount of earnout payable				$ 18,600
Number of completed acquisitions				2

ACQUISITIONS (Fair Values of Ne

ACQUISITIONS (Fair Values of Net Assets Acquired and Liabilities Assumed) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Apr. 30, 2019	Dec. 31, 2018	Nov. 01, 2018	Mar. 15, 2018
Business Acquisition [Line Items]
Goodwill	$ 211,956	$ 195,043		$ 166,832
Continuum
Business Acquisition [Line Items]
Cash and cash equivalents						$ 2,251
Trade receivables and contract assets						9,139
Prepaid and other current assets						936
Goodwill						26,617
Intangible assets						14,450
Property and equipment and other noncurrent assets						8,902
Total assets acquired						62,295
Accounts payable, accrued expenses and other current liabilities						3,746
Long-term debt (Note 9)						3,220
Other noncurrent liabilities						490
Total liabilities assumed						7,456
Net assets acquired						$ 54,839
Think
Business Acquisition [Line Items]
Cash and cash equivalents					$ 2,344
Trade receivables and contract assets					2,637
Prepaid and other current assets					900
Goodwill					20,477
Intangible assets					6,882
Property and equipment and other noncurrent assets					1,214
Total assets acquired					34,454
Accounts payable, accrued expenses and other current liabilities					2,025
Long-term debt (Note 9)					0
Other noncurrent liabilities					0
Total liabilities assumed					2,025
Net assets acquired					$ 32,429
test IO
Business Acquisition [Line Items]
Cash and cash equivalents			$ 663
Trade receivables and contract assets			621
Prepaid and other current assets			150
Goodwill			11,926
Intangible assets			6,219
Property and equipment and other noncurrent assets			305
Total assets acquired			19,884
Accounts payable, accrued expenses and other current liabilities			993
Long-term debt (Note 9)			0
Other noncurrent liabilities			1,568
Total liabilities assumed			2,561
Net assets acquired			$ 17,323
Other 2019 Acquisitions
Business Acquisition [Line Items]
Intangible assets		$ 7,500
2020 Acquisitions
Business Acquisition [Line Items]
Intangible assets	$ 7,300

ACQUISITIONS (Purchase Accounti

ACQUISITIONS (Purchase Accounting Adjustments) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Continuum
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustments [Abstract]
Purchase price adjustment			$ (100)
Total net assets purchase accounting adjustment			(100)
Think
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustments [Abstract]
Purchase price adjustment		$ 200
Increase in deferred tax assets		1,500
Goodwill purchase accounting adjustment			(2,043)
Total net assets purchase accounting adjustment		200
test IO
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustments [Abstract]
Purchase price adjustment		100
Intangible assets purchase accounting adjustment		(100)
Goodwill purchase accounting adjustment	$ (200)	(226)	$ 100
Total net assets purchase accounting adjustment		100
Other 2019 Acquisitions
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustments [Abstract]
Goodwill purchase accounting adjustment		$ 499

ACQUISITIONS (Fair Values and U

ACQUISITIONS (Fair Values and Useful Lives of Intangible Assets Acquired) (Details) - USD ($) $ in Thousands	Apr. 30, 2019	Nov. 01, 2018	Mar. 15, 2018
Continuum
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets acquired, amount			$ 14,450
Think
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets acquired, amount		$ 6,882
test IO
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets acquired, amount	$ 6,219
Customer relationships | Continuum
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted average useful life (in years)			6 years 6 months
Finite-lived intangible assets acquired, amount			$ 5,800
Customer relationships | Think
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted average useful life (in years)		7 years
Finite-lived intangible assets acquired, amount		$ 6,117
Customer relationships | test IO
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted average useful life (in years)	7 years
Finite-lived intangible assets acquired, amount	$ 2,456
Favorable lease | Continuum
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted average useful life (in years)			11 years 2 months 12 days
Finite-lived intangible assets acquired, amount			$ 5,500
Favorable lease | Think
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets acquired, amount		0
Favorable lease | test IO
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets acquired, amount	$ 0
Software | Continuum
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets acquired, amount			$ 0
Software | Think
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets acquired, amount		0
Software | test IO
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted average useful life (in years)	6 years
Finite-lived intangible assets acquired, amount	$ 3,461
Contract royalties | Continuum
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted average useful life (in years)			8 years
Finite-lived intangible assets acquired, amount			$ 1,900
Contract royalties | Think
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets acquired, amount		$ 0
Contract royalties | test IO
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets acquired, amount	$ 0
Trade names | Continuum
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted average useful life (in years)			5 years
Finite-lived intangible assets acquired, amount			$ 1,250
Trade names | Think
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted average useful life (in years)		5 years
Finite-lived intangible assets acquired, amount		$ 765
Trade names | test IO
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted average useful life (in years)	4 years
Finite-lived intangible assets acquired, amount	$ 302

ACQUISITIONS (Income Statement

ACQUISITIONS (Income Statement Effect) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Business Acquisition [Line Items]
Revenues	$ 723,493	$ 652,243	$ 632,383	$ 651,359	$ 632,775	$ 588,103	$ 551,587	$ 521,333	$ 2,659,478	$ 2,293,798	$ 1,842,912
2020 Acquisitions
Business Acquisition [Line Items]
Revenues									$ 6,000

GOODWILL AND INTANGIBLE ASSET_3

GOODWILL AND INTANGIBLE ASSETS, NET (Goodwill Roll Forward) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Goodwill [Roll Forward]
Balance beginning of period		$ 195,043	$ 166,832
Effect of net foreign currency exchange rate changes		3,695	1,317
Balance end of period		211,956	195,043
North America Segment
Goodwill [Roll Forward]
Balance beginning of period		113,426	103,542
Effect of net foreign currency exchange rate changes		582	80
Balance end of period		121,132	113,426
Europe Segment
Goodwill [Roll Forward]
Balance beginning of period		80,873	63,290
Effect of net foreign currency exchange rate changes		3,160	1,231
Balance end of period		90,106	80,873
Russia Segment
Goodwill [Roll Forward]
Balance beginning of period		744	0
Effect of net foreign currency exchange rate changes		(47)	6
Balance end of period		718	744
test IO
Goodwill [Roll Forward]
Acquisition			12,150
Purchase accounting adjustments	$ (200)	(226)	100
test IO | North America Segment
Goodwill [Roll Forward]
Acquisition			3,301
Purchase accounting adjustments		863
test IO | Europe Segment
Goodwill [Roll Forward]
Acquisition			8,849
Purchase accounting adjustments		(1,089)
test IO | Russia Segment
Goodwill [Roll Forward]
Acquisition			0
Purchase accounting adjustments		0
Other 2019 Acquisitions
Goodwill [Roll Forward]
Acquisition			16,787
Purchase accounting adjustments		499
Other 2019 Acquisitions | North America Segment
Goodwill [Roll Forward]
Acquisition			6,503
Purchase accounting adjustments		219
Other 2019 Acquisitions | Europe Segment
Goodwill [Roll Forward]
Acquisition			9,546
Purchase accounting adjustments		259
Other 2019 Acquisitions | Russia Segment
Goodwill [Roll Forward]
Acquisition			738
Purchase accounting adjustments		21
Think
Goodwill [Roll Forward]
Purchase accounting adjustments			(2,043)
Think | North America Segment
Goodwill [Roll Forward]
Purchase accounting adjustments			0
Think | Europe Segment
Goodwill [Roll Forward]
Purchase accounting adjustments			(2,043)
Think | Russia Segment
Goodwill [Roll Forward]
Purchase accounting adjustments			$ 0
2020 Acquisitions
Goodwill [Roll Forward]
Acquisition		12,945
2020 Acquisitions | North America Segment
Goodwill [Roll Forward]
Acquisition		6,042
2020 Acquisitions | Europe Segment
Goodwill [Roll Forward]
Acquisition		6,903
2020 Acquisitions | Russia Segment
Goodwill [Roll Forward]
Acquisition		$ 0

GOODWILL AND INTANGIBLE ASSET_4

GOODWILL AND INTANGIBLE ASSETS, NET (Goodwill Accumulated Impaitment Losses) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
North America Segment
Goodwill [Line Items]
Accumulated impairment loss	$ 0	$ 0	$ 0
Europe Segment
Goodwill [Line Items]
Accumulated impairment loss	0	0	0
Russia Segment
Goodwill [Line Items]
Accumulated impairment loss	$ 2.2	$ 2.2	$ 2.2

GOODWILL AND INTANGIBLE ASSET_5

GOODWILL AND INTANGIBLE ASSETS, NET (Intangible Assets Components and Amortization Expense Recognized) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 109,030	$ 100,458
Accumulated amortization	(57,055)	(44,200)
Net  carrying amount	51,975	56,258
Amortization of purchased intangibles	$ 12,340	$ 9,914	$ 8,511
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Weighted average life at acquisition (in years)	9 years	9 years
Gross carrying amount	$ 94,169	$ 87,489
Accumulated amortization	(49,415)	(38,526)
Net  carrying amount	44,754	48,963
Amortization of purchased intangibles	$ 10,478	$ 8,743	7,637
Software
Finite-Lived Intangible Assets [Line Items]
Weighted average life at acquisition (in years)	6 years	6 years
Gross carrying amount	$ 6,309	$ 4,472
Accumulated amortization	(1,633)	(486)
Net  carrying amount	4,676	3,986
Amortization of purchased intangibles	$ 1,068	$ 486	0
Trade names
Finite-Lived Intangible Assets [Line Items]
Weighted average life at acquisition (in years)	5 years	5 years
Gross carrying amount	$ 6,495	$ 6,439
Accumulated amortization	(5,273)	(4,753)
Net  carrying amount	1,222	1,686
Amortization of purchased intangibles	$ 495	$ 447	266
Contract royalties
Finite-Lived Intangible Assets [Line Items]
Weighted average life at acquisition (in years)	8 years	8 years
Gross carrying amount	$ 1,900	$ 1,900
Accumulated amortization	(673)	(435)
Net  carrying amount	1,227	1,465
Amortization of purchased intangibles	$ 238	$ 238	198
Assembled workforce
Finite-Lived Intangible Assets [Line Items]
Weighted average life at acquisition (in years)	3 years	3 years
Gross carrying amount	$ 157	$ 158
Accumulated amortization	(61)	0
Net  carrying amount	96	158
Amortization of purchased intangibles	61	0	0
Favorable lease
Finite-Lived Intangible Assets [Line Items]
Amortization of purchased intangibles	$ 0	$ 0	$ 410

GOODWILL AND INTANGIBLE ASSET_6

GOODWILL AND INTANGIBLE ASSETS, NET (Estimated Amortization Expense) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
2021	$ 12,585
2022	12,426
2023	11,115
2024	8,586
2025	5,543
Thereafter	1,720
Total	$ 51,975	$ 56,258

FAIR VALUE MEASUREMENTS (Assets

FAIR VALUE MEASUREMENTS (Assets and Liabilities at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Liabilities, Fair Value Disclosure [Abstract]
Contingent consideration	$ 7,119	$ 3,876	$ 8,390
Recurring
Assets, Fair Value Disclosure [Abstract]
Total assets measured at fair value on a recurring basis	4,955	1,910
Liabilities, Fair Value Disclosure [Abstract]
Contingent consideration	7,470	10,495
Total financial liabilities measured at fair value on a recurring basis	7,713	10,738
Recurring | Foreign exchange contract
Assets, Fair Value Disclosure [Abstract]
Derivative asset	4,955	1,910
Liabilities, Fair Value Disclosure [Abstract]
Derivative liabilities	243	243
Recurring | Level 1
Assets, Fair Value Disclosure [Abstract]
Total assets measured at fair value on a recurring basis	0	0
Liabilities, Fair Value Disclosure [Abstract]
Contingent consideration	0	0
Total financial liabilities measured at fair value on a recurring basis	0	0
Recurring | Level 1 | Foreign exchange contract
Assets, Fair Value Disclosure [Abstract]
Derivative asset	0	0
Liabilities, Fair Value Disclosure [Abstract]
Derivative liabilities	0	0
Recurring | Level 2
Assets, Fair Value Disclosure [Abstract]
Total assets measured at fair value on a recurring basis	4,955	1,910
Liabilities, Fair Value Disclosure [Abstract]
Contingent consideration	0	0
Total financial liabilities measured at fair value on a recurring basis	243	243
Recurring | Level 2 | Foreign exchange contract
Assets, Fair Value Disclosure [Abstract]
Derivative asset	4,955	1,910
Liabilities, Fair Value Disclosure [Abstract]
Derivative liabilities	243	243
Recurring | Level 3
Assets, Fair Value Disclosure [Abstract]
Total assets measured at fair value on a recurring basis	0	0
Liabilities, Fair Value Disclosure [Abstract]
Contingent consideration	7,470	10,495
Total financial liabilities measured at fair value on a recurring basis	7,470	10,495
Recurring | Level 3 | Foreign exchange contract
Assets, Fair Value Disclosure [Abstract]
Derivative asset	0	0
Liabilities, Fair Value Disclosure [Abstract]
Derivative liabilities	$ 0	$ 0

FAIR VALUE MEASUREMENTS (Narrat

FAIR VALUE MEASUREMENTS (Narrative) (Details) $ in Thousands	Nov. 01, 2018USD ($)	Mar. 15, 2018USD ($)	Jun. 30, 2020USD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Business Acquisition, Contingent Consideration [Line Items]
Contingent consideration				$ 7,119	$ 3,876	$ 8,390
Cash payment to extinguish the earnout obligation				(7,004)	(1,104)	0
Continuum
Business Acquisition, Contingent Consideration [Line Items]
Estimated future operating results, period		12 months
Contingent consideration		$ 2,400
Contingent consideration adjustment					(400)	$ (900)
Cash payment to extinguish the earnout obligation			$ (1,100)
Think
Business Acquisition, Contingent Consideration [Line Items]
Estimated future operating results, period	12 months
Contingent consideration	$ 6,000
Contingent consideration adjustment					$ 2,200
Cash payment to extinguish the earnout obligation				(7,900)
Other 2019 Acquisitions
Business Acquisition, Contingent Consideration [Line Items]
Cash payment to extinguish the earnout obligation				(1,800)
2020 Acquisitions
Business Acquisition, Contingent Consideration [Line Items]
Contingent consideration				$ 5,300
Minimum | Other 2019 Acquisitions
Business Acquisition, Contingent Consideration [Line Items]
Estimated future operating results, period					12 months
Minimum | Discount rate | 2020 Acquisitions
Business Acquisition, Contingent Consideration [Line Items]
Measurement input to determine fair value of contingent consideration				0.155
Maximum | Other 2019 Acquisitions
Business Acquisition, Contingent Consideration [Line Items]
Estimated future operating results, period					24 months
Maximum | Discount rate | 2020 Acquisitions
Business Acquisition, Contingent Consideration [Line Items]
Measurement input to determine fair value of contingent consideration				0.175

FAIR VALUE MEASUREMENTS (Reconc

FAIR VALUE MEASUREMENTS (Reconciliation of Acquisition-Related Contractual Contingent Liabilities Using Significant Unobservable Inputs) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Continuum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Changes in fair value of contingent consideration included in Interest and other income, net		$ (400)	$ (900)
Think
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Changes in fair value of contingent consideration included in Interest and other income, net		2,200
Level 3
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Contractual contingent liabilities, beginning of period	$ 10,495	7,468	0
Payment of contingent consideration for previously acquired businesses	9,619	1,104
Effect of net foreign currency exchange rate changes		255	(22)
Contractual contingent liabilities, end of period	7,470	10,495	7,468
Level 3 | Interest and Other Income, net
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Changes in fair value of contingent consideration included in Interest and other income, net	1,827	1,776	(900)
Level 3 | Continuum
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Acquisition date fair value of contingent consideration			2,400
Effect of net foreign currency exchange rate changes	(525)
Level 3 | Think
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Acquisition date fair value of contingent consideration			$ 5,990
Level 3 | Other 2019 Acquisitions
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Acquisition date fair value of contingent consideration		$ 2,100
Level 3 | 2020 Acquisitions
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Acquisition date fair value of contingent consideration	$ 5,292

FAIR VALUE MEASUREMENTS (Report

FAIR VALUE MEASUREMENTS (Reported Amounts and Estimated Fair Values of the Financial Assets and Liabilities for Which Disclosure of Fair Value is Required) (Details) - Nonrecurring - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Balance
Assets, Fair Value Disclosure [Abstract]
Cash equivalents	$ 153,783	$ 417,819
Restricted cash	1,390	1,136
Employee loans	794	2,434
Balance | Revolving credit facility | 2017 Credit Facility
Liabilities, Fair Value Disclosure [Abstract]
Borrowings	25,007	25,017
Balance | Money market funds
Assets, Fair Value Disclosure [Abstract]
Cash equivalents	153,783	407,817
Balance | Time deposits
Assets, Fair Value Disclosure [Abstract]
Cash equivalents		10,002
Short-term investments	60,007
Estimated Fair Value
Assets, Fair Value Disclosure [Abstract]
Cash equivalents	153,783	417,819
Restricted cash	1,390	1,136
Employee loans	794	2,434
Estimated Fair Value | Revolving credit facility | 2017 Credit Facility
Liabilities, Fair Value Disclosure [Abstract]
Borrowings	25,007	25,017
Estimated Fair Value | Money market funds
Assets, Fair Value Disclosure [Abstract]
Cash equivalents	153,783	407,817
Estimated Fair Value | Time deposits
Assets, Fair Value Disclosure [Abstract]
Cash equivalents		10,002
Short-term investments	60,007
Estimated Fair Value | Level 1
Assets, Fair Value Disclosure [Abstract]
Cash equivalents	153,783	407,817
Restricted cash	1,390	1,136
Employee loans	0	0
Estimated Fair Value | Level 1 | Revolving credit facility | 2017 Credit Facility
Liabilities, Fair Value Disclosure [Abstract]
Borrowings	0	0
Estimated Fair Value | Level 1 | Money market funds
Assets, Fair Value Disclosure [Abstract]
Cash equivalents	153,783	407,817
Estimated Fair Value | Level 1 | Time deposits
Assets, Fair Value Disclosure [Abstract]
Cash equivalents		0
Short-term investments	0
Estimated Fair Value | Level 2
Assets, Fair Value Disclosure [Abstract]
Cash equivalents	0	10,002
Restricted cash	0	0
Employee loans	0	0
Estimated Fair Value | Level 2 | Revolving credit facility | 2017 Credit Facility
Liabilities, Fair Value Disclosure [Abstract]
Borrowings	25,007	25,017
Estimated Fair Value | Level 2 | Money market funds
Assets, Fair Value Disclosure [Abstract]
Cash equivalents	0	0
Estimated Fair Value | Level 2 | Time deposits
Assets, Fair Value Disclosure [Abstract]
Cash equivalents		10,002
Short-term investments	60,007
Estimated Fair Value | Level 3
Assets, Fair Value Disclosure [Abstract]
Cash equivalents	0	0
Restricted cash	0	0
Employee loans	794	2,434
Estimated Fair Value | Level 3 | Revolving credit facility | 2017 Credit Facility
Liabilities, Fair Value Disclosure [Abstract]
Borrowings	0	0
Estimated Fair Value | Level 3 | Money market funds
Assets, Fair Value Disclosure [Abstract]
Cash equivalents	0	0
Estimated Fair Value | Level 3 | Time deposits
Assets, Fair Value Disclosure [Abstract]
Cash equivalents		$ 0
Short-term investments	$ 0

FAIR VALUE MEASUREMENTS (Non-Ma

FAIR VALUE MEASUREMENTS (Non-Marketable Securities Without Readily Determinable Fair Values) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Other noncurrent assets
Equity Securities without Readily Determinable Fair Value [Line Items]
Carrying amount of investments in equity securities	$ 25	$ 5.8

DERIVATIVE FINANCIAL INSTRUME_3

DERIVATIVE FINANCIAL INSTRUMENTS (Fair Value of Derivative Instruments) (Details) - Foreign exchange contract - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Financial collateral required to be posted	$ 0
Designated as hedging instrument | Prepaid and other current assets
Derivatives, Fair Value [Line Items]
Asset derivatives	4,955	$ 1,910
Designated as hedging instrument | Accrued expenses and other current liabilities
Derivatives, Fair Value [Line Items]
Liability derivatives	$ 243	$ 243

PROPERTY AND EQUIPMENT, NET (Co

PROPERTY AND EQUIPMENT, NET (Components of Property and Equipment and Depreciation) (Details) - USD ($) $ in Thousands	Nov. 01, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property and equipment, gross		$ 297,314	$ 259,566
Less accumulated depreciation and amortization		(127,781)	(94,307)
Total		169,533	165,259	$ 102,646
Depreciation and amortization expense		50,500	35,400	28,500
Payments to acquire an office building		$ (68,793)	(99,308)	(37,574)
Computer hardware
Property, Plant and Equipment [Line Items]
Weighted average useful life (in years)		3 years
Property and equipment, gross		$ 117,333	96,286
Buildings
Property, Plant and Equipment [Line Items]
Weighted average useful life (in years)		46 years
Property and equipment, gross		$ 52,007	51,300
Leasehold improvements
Property, Plant and Equipment [Line Items]
Weighted average useful life (in years)		7 years
Property and equipment, gross		$ 39,675	30,634
Purchased computer software
Property, Plant and Equipment [Line Items]
Weighted average useful life (in years)		3 years
Property and equipment, gross		$ 31,993	32,115
Furniture, fixture and other equipment
Property, Plant and Equipment [Line Items]
Weighted average useful life (in years)		7 years
Property and equipment, gross		$ 31,859	28,193
Office equipment
Property, Plant and Equipment [Line Items]
Weighted average useful life (in years)		7 years
Property and equipment, gross		$ 20,971	18,901
Land improvements
Property, Plant and Equipment [Line Items]
Weighted average useful life (in years)		18 years
Property and equipment, gross		$ 2,137	2,137
Land
Property, Plant and Equipment [Line Items]
Property and equipment, gross		1,339	0
Assets leased to third parties under operating lease
Property, Plant and Equipment [Line Items]
Property and equipment, gross		6,700	10,700
Less accumulated depreciation and amortization		(200)	(100)
Depreciation and amortization expense		200	100
Belarus
Property, Plant and Equipment [Line Items]
Total		$ 73,988	$ 75,984	$ 50,085
Belarus | Buildings
Property, Plant and Equipment [Line Items]
Payments to acquire an office building	$ (18,900)

ACCRUED EXPENSES AND OTHER CU_3

ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES (Components of Accrued expenses and other current liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Payables and Accruals [Abstract]
Value added taxes payable	$ 34,522	$ 24,016
Deferred revenue	17,383	9,132
Contingent consideration, current (Note 4)	1,125	10,057
Other current liabilities and accrued expenses	26,660	39,271
Total	$ 79,690	$ 82,476

LEASES (Narrative) (Details)

LEASES (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020USD ($)
Lessee, Lease, Description [Line Items]
Operating lease description	The Company leases office space, corporate apartments, office equipment, and vehicles.
Terms and conditions of variable lease payments	Many of the Company’s leases contain variable payments including changes in base rent and charges for common area maintenance or other miscellaneous expenses.
Existence of options to extend	true
Existence of option to terminate	true
Existence of material residual value guarantees	false
Description of material restrictive covenants imposed by operating lease	There were no lease agreements that contained material restrictive covenants
Description of lease agreements signed with related parties	There were no material lease agreements signed with related parties as of December 31, 2020.
Description of operating lease agreements that have not yet commenced	As of December 31, 2020, the Company had committed to payments of $1.0 million related to operating lease agreements that had not yet commenced as of December 31, 2020. These operating leases will commence on various dates during 2021 with lease terms ranging from 1 year to 5 years.
Description of finance lease agreements that have not yet commenced	The Company does not have any material finance lease agreements that had not yet commenced.
Commitments related to operating lease agreements that have not yet commenced	$ 1
Minimum
Lessee, Lease, Description [Line Items]
Remaining lease term	29 days
Lease term of lease agreements that have not yet commenced	1 year
Maximum
Lessee, Lease, Description [Line Items]
Remaining lease term	10 years 4 months 24 days
Lease term of lease agreements that have not yet commenced	5 years

LEASES (Components of Lease Exp

LEASES (Components of Lease Expenses) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Lease, Cost [Line Items]
Total lease cost	$ 81,370	$ 75,340
Selling, general and administrative expenses
Lease, Cost [Line Items]
Operating lease cost	73,740	62,740
Variable lease cost	6,461	8,730
Short-term lease cost	$ 1,169	$ 3,870

LEASES (Rent Expenses for Prior

LEASES (Rent Expenses for Prior Periods) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)
Leases [Abstract]
Operating lease expense	$ 46.9

LEASES (Supplemental Cash Flow

LEASES (Supplemental Cash Flow Information) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows used for operating leases	$ 70,012	$ 59,952
Right-of-use assets obtained in exchange for lease obligations:
Operating leases	50,949	107,822
Non-cash net increase due to lease modifications:
Operating lease right-of-use assets	7,876	10,124
Operating lease liabilities	$ 7,861	$ 10,192

LEASES (Weighted Average Remain

LEASES (Weighted Average Remaining Lease Term and Discount Rate) (Details)	Dec. 31, 2020	Dec. 31, 2019
Weighted average remaining lease term, in years:
Operating leases	5 years 10 months 24 days	6 years 1 month 6 days
Weighted average discount rate:
Operating leases	2.90%	3.60%

LEASES (Maturity of Operating L

LEASES (Maturity of Operating Lease Liabilities) (Details) $ in Thousands	Dec. 31, 2020USD ($)
Leases [Abstract]
2021	$ 66,585
2022	50,147
2023	37,268
2024	32,400
2025	22,859
Thereafter	52,531
Total lease payments	261,790
Less: imputed interest	(20,427)
Total	$ 241,363

LONG-TERM DEBT (Narrative) (Det

LONG-TERM DEBT (Narrative) (Details) - USD ($) $ in Thousands	Mar. 15, 2018	May 24, 2017	Mar. 31, 2018	Dec. 31, 2020	Dec. 31, 2019
Continuum
Debt Instrument [Line Items]
Maturity date	Mar. 31, 2029
Long-term debt	$ 3,400
Contractual interest rate	8.00%
Repayments of debt			$ 3,400
Revolving credit facility | 2017 Credit Facility
Debt Instrument [Line Items]
Maturity date		May 24, 2022
Revolving credit facility | 2017 Credit Facility | LIBOR
Debt Instrument [Line Items]
Variable interest rate spread		1.00%
Revolving credit facility | 2017 Credit Facility | Overnight Bank Funding Rate
Debt Instrument [Line Items]
Variable interest rate spread		0.50%
Revolving credit facility | 2017 Credit Facility | U.S. Dollars
Debt Instrument [Line Items]
Line of credit, current borrowing capacity		$ 300,000
Line of credit, maximum borrowing capacity		400,000
Outstanding debt				$ 25,000	$ 25,000
Interest rate				1.20%	2.80%
Available borrowing capacity				$ 275,000	$ 274,697
Revolving credit facility | 2017 Credit Facility | U.S. Dollars | Maximum
Debt Instrument [Line Items]
Line of credit, current borrowing capacity				300,000	300,000
Revolving credit facility | 2017 Credit Facility | Other currencies, excluding U.S. dollars
Debt Instrument [Line Items]
Line of credit, maximum borrowing capacity		$ 100,000
Standby letters of credit | 2017 Credit Facility
Debt Instrument [Line Items]
Irrevocable standby letters of credit				$ 0	$ 303

PENSION AND POSTRETIREMENT BE_2

PENSION AND POSTRETIREMENT BENEFITS (Defined Contribution Pension Plan) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Retirement Benefits [Abstract]
Defined contribution plan expenses recognized	$ 16	$ 14.8	$ 6.5

PENSION AND POSTRETIREMENT BE_3

PENSION AND POSTRETIREMENT BENEFITS (Defined Benefit Pension Plans) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan expenses recognized	$ 4.3	$ 1.4	$ 2.6
Unfunded status of defined benefit plan	(6.4)	(3.9)
Accumulated Other Comprehensive (Loss)/ Income
Defined Benefit Plan Disclosure [Line Items]
Actuarial loss	(1.3)
Accrued compensation and benefits expenses
Defined Benefit Plan Disclosure [Line Items]
Unfunded status of defined benefit plan	(1)	(0.3)
Other noncurrent liabilities
Defined Benefit Plan Disclosure [Line Items]
Unfunded status of defined benefit plan	$ (5.4)	$ (3.6)

REVENUES (Disaggregation of Rev

REVENUES (Disaggregation of Revenues) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Revenues	$ 723,493	$ 652,243	$ 632,383	$ 651,359	$ 632,775	$ 588,103	$ 551,587	$ 521,333	$ 2,659,478	$ 2,293,798	$ 1,842,912
Transferred over time
Disaggregation of Revenue [Line Items]
Revenues									2,650,991	2,291,245	1,841,242
Transferred at a point of time
Disaggregation of Revenue [Line Items]
Revenues									8,487	2,553	1,670
Time-and-material
Disaggregation of Revenue [Line Items]
Revenues									2,291,004	1,990,653	1,652,897
Fixed-price
Disaggregation of Revenue [Line Items]
Revenues									352,012	294,650	184,251
Licensing
Disaggregation of Revenue [Line Items]
Revenues									11,139	5,081	4,097
Other revenues
Disaggregation of Revenue [Line Items]
Revenues									5,323	3,414	1,667
Business Information & Media
Disaggregation of Revenue [Line Items]
Revenues									560,680	420,923	324,033
Financial Services
Disaggregation of Revenue [Line Items]
Revenues									555,235	500,872	423,977
Software & Hi-Tech
Disaggregation of Revenue [Line Items]
Revenues									496,813	433,398	350,815
Travel & Consumer
Disaggregation of Revenue [Line Items]
Revenues									458,789	439,358	393,643
Life Sciences & Healthcare
Disaggregation of Revenue [Line Items]
Revenues									296,313	248,452	171,703
Emerging Verticals
Disaggregation of Revenue [Line Items]
Revenues									291,648	250,795	178,741
North America
Disaggregation of Revenue [Line Items]
Revenues									1,595,136	1,390,015	1,099,167
Europe
Disaggregation of Revenue [Line Items]
Revenues									879,842	746,866	612,472
CIS
Disaggregation of Revenue [Line Items]
Revenues									114,702	100,471	81,703
APAC
Disaggregation of Revenue [Line Items]
Revenues									69,798	56,446	49,570
North America Segment
Disaggregation of Revenue [Line Items]
Revenues									1,601,820	1,380,944	1,076,979
North America Segment | Transferred over time
Disaggregation of Revenue [Line Items]
Revenues									1,595,786	1,379,256	1,076,084
North America Segment | Transferred at a point of time
Disaggregation of Revenue [Line Items]
Revenues									6,034	1,688	895
North America Segment | Time-and-material
Disaggregation of Revenue [Line Items]
Revenues									1,440,635	1,247,979	983,436
North America Segment | Fixed-price
Disaggregation of Revenue [Line Items]
Revenues									151,769	127,926	89,831
North America Segment | Licensing
Disaggregation of Revenue [Line Items]
Revenues									8,027	3,626	2,748
North America Segment | Other revenues
Disaggregation of Revenue [Line Items]
Revenues									1,389	1,413	964
North America Segment | Business Information & Media
Disaggregation of Revenue [Line Items]
Revenues									334,063	262,448	251,081
North America Segment | Financial Services
Disaggregation of Revenue [Line Items]
Revenues									199,594	184,469	112,444
North America Segment | Software & Hi-Tech
Disaggregation of Revenue [Line Items]
Revenues									419,895	354,023	269,067
North America Segment | Travel & Consumer
Disaggregation of Revenue [Line Items]
Revenues									221,977	198,264	177,910
North America Segment | Life Sciences & Healthcare
Disaggregation of Revenue [Line Items]
Revenues									260,518	224,925	151,418
North America Segment | Emerging Verticals
Disaggregation of Revenue [Line Items]
Revenues									165,773	156,815	115,059
North America Segment | North America
Disaggregation of Revenue [Line Items]
Revenues									1,546,093	1,344,040	1,046,232
North America Segment | Europe
Disaggregation of Revenue [Line Items]
Revenues									45,733	27,042	16,679
North America Segment | CIS
Disaggregation of Revenue [Line Items]
Revenues									7,817	8,583	8,437
North America Segment | APAC
Disaggregation of Revenue [Line Items]
Revenues									2,177	1,279	5,631
Europe Segment
Disaggregation of Revenue [Line Items]
Revenues									947,305	820,717	692,785
Europe Segment | Transferred over time
Disaggregation of Revenue [Line Items]
Revenues									946,379	819,913	692,023
Europe Segment | Transferred at a point of time
Disaggregation of Revenue [Line Items]
Revenues									926	804	762
Europe Segment | Time-and-material
Disaggregation of Revenue [Line Items]
Revenues									790,203	688,605	628,707
Europe Segment | Fixed-price
Disaggregation of Revenue [Line Items]
Revenues									151,718	128,977	62,078
Europe Segment | Licensing
Disaggregation of Revenue [Line Items]
Revenues									1,526	1,230	1,332
Europe Segment | Other revenues
Disaggregation of Revenue [Line Items]
Revenues									3,858	1,905	668
Europe Segment | Business Information & Media
Disaggregation of Revenue [Line Items]
Revenues									224,922	157,844	72,898
Europe Segment | Financial Services
Disaggregation of Revenue [Line Items]
Revenues									278,355	244,284	252,196
Europe Segment | Software & Hi-Tech
Disaggregation of Revenue [Line Items]
Revenues									73,288	77,377	79,121
Europe Segment | Travel & Consumer
Disaggregation of Revenue [Line Items]
Revenues									220,448	229,523	208,266
Europe Segment | Life Sciences & Healthcare
Disaggregation of Revenue [Line Items]
Revenues									35,347	23,444	20,272
Europe Segment | Emerging Verticals
Disaggregation of Revenue [Line Items]
Revenues									114,945	88,245	60,032
Europe Segment | North America
Disaggregation of Revenue [Line Items]
Revenues									45,553	45,859	52,860
Europe Segment | Europe
Disaggregation of Revenue [Line Items]
Revenues									834,033	719,548	595,741
Europe Segment | CIS
Disaggregation of Revenue [Line Items]
Revenues									98	143	336
Europe Segment | APAC
Disaggregation of Revenue [Line Items]
Revenues									67,621	55,167	43,848
Russia Segment
Disaggregation of Revenue [Line Items]
Revenues									110,353	92,137	73,148
Russia Segment | Transferred over time
Disaggregation of Revenue [Line Items]
Revenues									108,826	92,076	73,135
Russia Segment | Transferred at a point of time
Disaggregation of Revenue [Line Items]
Revenues									1,527	61	13
Russia Segment | Time-and-material
Disaggregation of Revenue [Line Items]
Revenues									60,166	54,069	40,754
Russia Segment | Fixed-price
Disaggregation of Revenue [Line Items]
Revenues									48,525	37,747	32,342
Russia Segment | Licensing
Disaggregation of Revenue [Line Items]
Revenues									1,586	225	17
Russia Segment | Other revenues
Disaggregation of Revenue [Line Items]
Revenues									76	96	35
Russia Segment | Business Information & Media
Disaggregation of Revenue [Line Items]
Revenues									1,695	631	54
Russia Segment | Financial Services
Disaggregation of Revenue [Line Items]
Revenues									77,286	72,119	59,337
Russia Segment | Software & Hi-Tech
Disaggregation of Revenue [Line Items]
Revenues									3,630	1,998	2,627
Russia Segment | Travel & Consumer
Disaggregation of Revenue [Line Items]
Revenues									16,364	11,571	7,467
Russia Segment | Life Sciences & Healthcare
Disaggregation of Revenue [Line Items]
Revenues									448	83	13
Russia Segment | Emerging Verticals
Disaggregation of Revenue [Line Items]
Revenues									10,930	5,735	3,650
Russia Segment | North America
Disaggregation of Revenue [Line Items]
Revenues									3,490	116	75
Russia Segment | Europe
Disaggregation of Revenue [Line Items]
Revenues									76	276	52
Russia Segment | CIS
Disaggregation of Revenue [Line Items]
Revenues									106,787	91,745	72,930
Russia Segment | APAC
Disaggregation of Revenue [Line Items]
Revenues									$ 0	$ 0	$ 91

REVENUES (Timing of Revenue Rec

REVENUES (Timing of Revenue Recognition) (Details) - Fixed-price $ in Thousands	Dec. 31, 2020USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Estimated revenues expected to be recognized in the future related to performance obligations	$ 7,988
Less than 1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Estimated revenues expected to be recognized in the future related to performance obligations	7,885
1 Year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Estimated revenues expected to be recognized in the future related to performance obligations	103
2 Years
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Estimated revenues expected to be recognized in the future related to performance obligations	0
3 Years
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Estimated revenues expected to be recognized in the future related to performance obligations	$ 0

REVENUES (Narrative) (Details)

REVENUES (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Change in Contract with Customer, Asset and Liability [Abstract]
Revenues from performance obligations satisfied in previous periods	$ 5	$ 7.8	$ 5.7
Accrued expenses and other current liabilities
Change in Contract with Customer, Liability [Abstract]
Revenues recognized	$ 8.6	$ 3.9

REVENUES (Contract Assets and L

REVENUES (Contract Assets and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Trade receivables and contract assets
Change in Contract with Customer, Asset and Liability [Abstract]
Contract assets	$ 7,700	$ 14,320
Accrued expenses and other current liabilities
Change in Contract with Customer, Asset and Liability [Abstract]
Contract liabilities	17,383	9,132
Other noncurrent liabilities
Change in Contract with Customer, Asset and Liability [Abstract]
Contract liabilities	$ 94	$ 5

STOCK-BASED COMPENSATION (Costs

STOCK-BASED COMPENSATION (Costs Related to Stock Compensation Plans) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 75,238	$ 72,036	$ 59,188
Cost of revenues (exclusive of depreciation and amortization)
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	32,785	37,580	27,245
Selling, general and administrative expenses
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 42,453	$ 34,456	$ 31,943

STOCK-BASED COMPENSATION (Equit

STOCK-BASED COMPENSATION (Equity Plans) (Details) - shares shares in Thousands	Jun. 11, 2015	Jan. 11, 2012	May 31, 2006	Dec. 31, 2020
2015 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for issuance (in shares)				4,549
Expiration period	10 years
2012 Directors Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for issuance (in shares)				524
Number of shares authorized for issuance (in shares)		600
Expiration period		10 years
2012 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration period		10 years
2006 Plan | Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration period			10 years

STOCK-BASED COMPENSATION (Stock

STOCK-BASED COMPENSATION (Stock Option Activity) (Details) - Stock Options - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Number of Options (in shares)
Options outstanding, beginning of period	3,323	4,083	4,902
Options granted	158	132	160
Options modified	0	18
Options exercised	(700)	(899)	(945)
Options forfeited/cancelled	(9)	(11)	(33)
Options expired			(1)
Options outstanding, end of period	2,772	3,323	4,083
Options vested and exercisable as of December 31, 2020	2,388
Options expected to vest as of December 31, 2020	362
Weighted Average Exercise Price (in dollars per share)
Options outstanding, beginning of period	$ 50.85	$ 44.54	$ 40.91
Options granted	187.76	169.13	112.81
Options modified	0	163.55
Options exercised	37.79	41.21	36.69
Options forfeited/cancelled	119.30	97.83	63.28
Options expired			25.72
Options outstanding, end of period	61.71	$ 50.85	$ 44.54
Options vested and exercisable as of December 31, 2020	46.99
Options expected to vest as of December 31, 2020	$ 152.22
Aggregate Intrinsic Value
Options outstanding, beginning of period	$ 536,015	$ 291,846	$ 326,064
Options outstanding, end of period	822,152	$ 536,015	$ 291,846
Options vested and exercisable as of December 31, 2020	743,582
Options expected to vest as of December 31, 2020	$ 74,548
Weighted Average Remaining Contractual Term (in years)
Options outstanding as of December 31, 2020	4 years 3 months 18 days
Options vested and exercisable as of December 31, 2020	3 years 8 months 12 days
Options expected to vest as of December 31, 2020	8 years 2 months 12 days

STOCK-BASED COMPENSATION (Black

STOCK-BASED COMPENSATION (Black Scholes Option Valuation Model Assumptions) (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Payment Arrangement [Abstract]
Expected volatility	36.90%	33.50%	33.80%
Expected term (in years)	6 years 3 months	6 years 3 months	6 years 3 months
Risk-free interest rate	0.50%	2.30%	2.70%
Expected dividends	0.00%	0.00%	0.00%

STOCK-BASED COMPENSATION (Sto_2

STOCK-BASED COMPENSATION (Stock Options Additional Information) (Details) - Stock Options - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average grant-date fair value	$ 68.53	$ 63.12	$ 43.42
Total intrinsic value of options exercised	$ 151.3	$ 121.1	$ 83.3
Vesting period (in years)	4 years
Unrecognized compensation cost net of estimated forfeitures	$ 15.1
Unrecognized compensation cost, period for recognition	2 years 8 months 12 days

STOCK-BASED COMPENSATION (Retri

STOCK-BASED COMPENSATION (Retricted Stock and Restricted Stock Units Activity) (Details) - $ / shares shares in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Service period | Equity classified award | Equity-settled award | Restricted stock
Number of Shares
Unvested awards outstanding, beginning of period	10	10	1	2
Awards granted		0	9	0
Awards modified		0	0	0
Awards vested		(1)	0	(1)
Awards forfeited/cancelled		0	0	0
Unvested awards outstanding, end of period		9	10	1
Weighted Average Grant Date Fair Value Per Share (in dollars per share)
Unvested awards outstanding, beginning of period	$ 162.96	$ 162.96	$ 63.10	$ 54.37
Awards granted		0	167.18	0
Awards modified		0	0	0
Awards vested		63.10	0	47.76
Awards forfeited/cancelled		0	0	0
Unvested awards outstanding, end of period		$ 167.18	$ 162.96	$ 63.10
Service period | Equity classified award | Equity-settled award | Restricted stock units
Number of Shares
Unvested awards outstanding, beginning of period	759	759	798	688
Awards granted		294	284	381
Awards modified		(1)	7	(3)
Awards vested		(317)	(287)	(218)
Awards forfeited/cancelled		(49)	(43)	(50)
Unvested awards outstanding, end of period		686	759	798
Weighted Average Grant Date Fair Value Per Share (in dollars per share)
Unvested awards outstanding, beginning of period	$ 122.48	$ 122.48	$ 92.13	$ 71.60
Awards granted		204.57	170.29	115.84
Awards modified		122.55	170.74	80.27
Awards vested		108.87	87.79	70.10
Awards forfeited/cancelled		148.11	114.45	86.97
Unvested awards outstanding, end of period		$ 162.15	$ 122.48	$ 92.13
Service period | Liability classified award | Cash-settled award | Restricted stock units
Number of Shares
Unvested awards outstanding, beginning of period	242	242	303	315
Awards granted		60	56	85
Awards modified		0	1	3
Awards vested		(122)	(111)	(92)
Awards forfeited/cancelled		(5)	(7)	(8)
Unvested awards outstanding, end of period		175	242	303
Weighted Average Grant Date Fair Value Per Share (in dollars per share)
Unvested awards outstanding, beginning of period	$ 105.40	$ 105.40	$ 83.99	$ 72.50
Awards granted		181.77	170.13	112.65
Awards modified		0	168.36	120.18
Awards vested		91.39	80.51	72.69
Awards forfeited/cancelled		113.94	94.77	81.40
Unvested awards outstanding, end of period		$ 141.16	$ 105.40	$ 83.99
Performance targets | Equity classified award | Equity-settled award | Restricted stock
Number of Shares
Unvested awards outstanding, beginning of period	9	9	0	0
Awards granted		0	9	0
Awards modified			0
Awards vested		0		0
Awards forfeited/cancelled				0
Unvested awards outstanding, end of period		9	9	0
Weighted Average Grant Date Fair Value Per Share (in dollars per share)
Unvested awards outstanding, beginning of period	$ 165.87	$ 165.87	$ 0	$ 0
Awards granted		0	165.87	0
Awards modified			0
Awards vested		0		0
Awards forfeited/cancelled				0
Unvested awards outstanding, end of period		$ 165.87	$ 165.87	$ 0
Performance targets | Equity classified award | Equity-settled award | Restricted stock units
Number of Shares
Unvested awards outstanding, beginning of period	0	0	30	0
Awards granted		31	0	45
Awards modified			(30)
Awards vested		(10)		(8)
Awards forfeited/cancelled				(7)
Unvested awards outstanding, end of period		21	0	30
Weighted Average Grant Date Fair Value Per Share (in dollars per share)
Unvested awards outstanding, beginning of period	$ 0	$ 0	$ 121.75	$ 0
Awards granted		210.44	0	121.75
Awards modified			121.75
Awards vested		177.81		121.75
Awards forfeited/cancelled				121.75
Unvested awards outstanding, end of period		$ 227.16	$ 0	$ 121.75
2020 Acquisitions | Service period | Equity classified award | Equity-settled award | Restricted stock units
Number of Shares
Awards granted		19
2020 Acquisitions | Service period | Liability classified award | Cash-settled award | Restricted stock units
Number of Shares
Awards granted		10
2020 Acquisitions | Performance targets | Equity classified award | Equity-settled award | Restricted stock units
Number of Shares
Awards granted		7
2019 Acquisitions | Service period | Equity classified award | Equity-settled award | Restricted stock
Number of Shares
Awards granted			9
2019 Acquisitions | Service period | Equity classified award | Equity-settled award | Restricted stock units
Number of Shares
Awards granted	6		22
2019 Acquisitions | Service period | Liability classified award | Cash-settled award | Restricted stock units
Number of Shares
Awards granted			7
2019 Acquisitions | Performance targets | Equity classified award | Equity-settled award | Restricted stock
Number of Shares
Awards granted			9
2019 Acquisitions | Performance targets | Equity classified award | Equity-settled award | Restricted stock units
Number of Shares
Awards granted		25

STOCK-BASED COMPENSATION (Fair

STOCK-BASED COMPENSATION (Fair Value of Restricted Stock and Restricted Stock Units Vested) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Service period
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of awards vested	$ 82,157	$ 66,633	$ 35,478
Performance targets
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of awards vested	3,282	0	1,046
Equity classified award | Service period | Equity-settled award | Restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of awards vested	101	73	142
Equity classified award | Service period | Equity-settled award | Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of awards vested	60,042	48,111	24,987
Equity classified award | Performance targets | Equity-settled award | Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of awards vested	3,282	0	1,046
Liability classified award | Service period | Cash-settled award | Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of awards vested	$ 22,014	$ 18,449	$ 10,349

STOCK-BASED COMPENSATION (Ret_2

STOCK-BASED COMPENSATION (Retricted Stock and Restricted Stock Units Additional Information) (Details) - USD ($) $ in Millions	Mar. 15, 2018	Dec. 31, 2018	Dec. 31, 2020	Dec. 31, 2019
Equity classified award | Performance targets | Equity-settled award | Restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost			$ 1
Unrecognized compensation cost, period for recognition			2 years 8 months 12 days
Equity classified award | Performance targets | Equity-settled award | Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost			$ 3.6
Unrecognized compensation cost, period for recognition			2 years 9 months 18 days
Equity classified award | Service period | Equity-settled award | Restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost			$ 0.8
Unrecognized compensation cost, period for recognition			1 year 8 months 12 days
Equity classified award | Service period | Equity-settled award | Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost			$ 76.3
Unrecognized compensation cost, period for recognition			2 years 8 months 12 days
Liability classified award | Service period | Cash-settled award | Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost			$ 32.3
Unrecognized compensation cost, period for recognition			2 years 3 months 18 days
Liability classified award | Service period | Cash-settled award | Restricted stock units | Accrued compensation and benefits expenses
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Liability associated with stock-based awards current			$ 26.8	$ 21.9
2020 Acquisitions | Performance targets | Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost			$ 0.5
Unrecognized compensation cost, period for recognition			2 years
Estimated future operating results, period			2 years
Vesting period (in years)			3 years
Future value of awards			$ 11.5
2019 Acquisitions | Equity classified award | Performance targets | Equity-settled award | Restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Estimated future operating results, period				12 months
Vesting period (in years)				4 years
Continuum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Estimated future operating results, period	12 months
Continuum | Equity classified award | Performance targets | Equity-settled award | Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award accelerated compensation cost		$ 0.8

INCOME TAXES (Income before Pro

INCOME TAXES (Income before Provision for Income Taxes) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income before provision for income taxes:
United States									$ 100,411	$ 65,370	$ 44,527
Foreign									278,068	234,156	205,246
Income before provision for income taxes	$ 102,020	$ 103,964	$ 76,076	$ 96,419	$ 84,797	$ 79,969	$ 70,510	$ 64,250	$ 378,479	$ 299,526	$ 249,773

INCOME TAXES (Provision for Inc

INCOME TAXES (Provision for Income Taxes) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Current
Federal									$ 19,249	$ 16,943	$ 10,814
State									7,022	3,610	4,123
Foreign									45,042	25,680	42,580
Deferred
Federal									(16,235)	(9,425)	(37,785)
State									(1,682)	(358)	(3,548)
Foreign									(2,077)	2,019	(6,667)
Total	$ 16,481	$ 14,532	$ 9,452	$ 10,854	$ 10,273	$ 12,967	$ 11,733	$ 3,496	$ 51,319	$ 38,469	$ 9,517

INCOME TAXES (U.S. Tax Act Effe

INCOME TAXES (U.S. Tax Act Effect) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Tax Cuts and Jobs Act, Transition Tax for Accumulated Foreign Earnings, Liability [Abstract]
Provisional charge adjustment			$ (4,900)
Transition tax provisional charge	$ 40,500
Tax Cuts and Jobs Act, Incomplete Accounting, Change in Tax Rate, Provisional Income Tax Expense (Benefit) [Abstract]
Total adjustment to deferred tax asset recorded		$ 900
Net income tax benefit resulting from U.S. foreign tax credit for withholding tax	0	$ 0	$ 4,850
Accumulated undistributed foreign earnings indefinitely reinvested	$ 1,039,000
United States
Effect of Tax Cuts and Jobs Act [Abstract]
Statutory income tax rate				35.00%
U.S. Tax Cuts and Jobs Act
Tax Cuts and Jobs Act, Transition Tax for Accumulated Foreign Earnings, Liability [Abstract]
Income tax rate on foreign cash and certain other net current assets			15.50%
Income tax rate on remaining earnings			8.00%
U.S. Tax Cuts and Jobs Act | United States
Effect of Tax Cuts and Jobs Act [Abstract]
Statutory income tax rate			21.00%
U.S. Tax Cuts and Jobs Act | Belarus
Tax Cuts and Jobs Act, Incomplete Accounting, Change in Tax Rate, Provisional Income Tax Expense (Benefit) [Abstract]
Net income tax benefit resulting from U.S. foreign tax credit for withholding tax			$ 4,900

INCOME TAXES (Effective Tax Rat

INCOME TAXES (Effective Tax Rate Reconciliation) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Provision for income taxes at federal statutory rate									$ 79,481	$ 62,898	$ 52,452
Impact from U.S. Tax Act
Impact from U.S. Tax Act									0	0	(4,009)
Entity classification election deferred tax asset impact									0	0	(25,962)
GILTI and BEAT U.S. taxes									191	(926)	1,526
Excess tax benefits relating to stock-based compensation									(36,646)	(28,385)	(17,370)
Subsidiary withholding tax liability and related foreign tax credit									0	0	(4,850)
Foreign tax expense and tax rate differential									(387)	(1,402)	(88)
Effect of permanent differences									3,507	3,264	2,724
State taxes, net of federal benefit									5,323	2,971	3,452
Stock-based compensation expense									44	571	652
Other									(194)	(522)	990
Entity classification election deferred tax asset impact									0	0	(25,962)
Total	$ 16,481	$ 14,532	$ 9,452	$ 10,854	$ 10,273	$ 12,967	$ 11,733	$ 3,496	$ 51,319	$ 38,469	$ 9,517
Effective tax rate									13.60%	12.80%	3.80%
Net deferred tax assets resulting from the change in tax status of foreign subsidiaries					$ 26,000					$ 26,000
ASU 2016-09
Impact from U.S. Tax Act
Excess tax benefit									$ 36,600	$ 28,400	$ 17,400

INCOME TAXES (Income Tax Holida

INCOME TAXES (Income Tax Holiday) (Details) - Foreign - Belarus - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Holiday [Line Items]
Income tax holiday description	In Belarus, member technology companies of High-Technologies Park, including the Company’s local subsidiary, have a full exemption from Belarus income tax on qualifying income through January 2049. However, beginning February 1, 2018, the earnings of the Company’s Belarus local subsidiary became subject to U. S. income taxation due to the Company’s decision to change the tax status of the subsidiary. There was no aggregate dollar benefit derived from this tax holiday for the years ended December 31, 2020 and 2019, and the aggregate dollar benefits derived from this tax holiday approximated $1.4 million for the year ended December 31, 2018. There was no impact on diluted net income per share for the years ended December 31, 2020 and 2019. The benefit the tax holiday had on diluted net income per share approximated $0.02 for the year ended December 31, 2018.
Income tax holiday termination date	January 2049
Aggregate dollar benefits from tax holiday	$ 0	$ 0	$ 1,400
Tax holiday benefit on diluted net income per share	$ 0	$ 0	$ 0.02

INCOME TAXES (Deferred Income T

INCOME TAXES (Deferred Income Taxes) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Deferred Tax Assets, Gross [Abstract]
Property and equipment	$ 8,164	$ 5,329
Intangible assets	827	574
Accrued expenses	50,639	41,457
Net operating loss carryforward	6,089	5,168
Deferred revenue	9,796	3,510
Stock-based compensation	30,112	29,596
Operating lease liabilities	51,519	7,438
Foreign tax credit	2,168	3,491
Foreign currency exchange	4,890	2,499
Other assets	1,252	1,533
Deferred tax assets	165,456	100,595
Less: valuation allowance	(5,485)	(3,877)
Total deferred tax assets	159,971	96,718
Deferred Tax Liabilities, Gross [Abstract]
Property and equipment	3,818	4,981
Intangible assets	12,018	11,364
Operating lease right-of-use assets	50,149	6,900
Accrued revenue and expenses	991	2,176
U.S. taxation of foreign subsidiaries	1,608	0
Foreign currency exchange	1,153	375
Other liabilities	1,095	437
Total deferred tax liabilities	70,832	26,233
Net deferred tax assets	89,139	70,485
Other noncurrent liabilities
Deferred Tax Liabilities, Gross [Abstract]
Deferred Income Tax Liabilities, Net	3,300	4,500
Business acquisitions
Deferred Tax Assets, Gross [Abstract]
Stock-based compensation	$ 6,100	$ 6,800
Business acquisitions | Minimum
Deferred Tax Assets, Gross [Abstract]
Amortization period of stock-based compensation for tax	10 years
Business acquisitions | Maximum
Deferred Tax Assets, Gross [Abstract]
Amortization period of stock-based compensation for tax	15 years

INCOME TAXES (Operating Loss Ca

INCOME TAXES (Operating Loss Carryforwards) (Details) $ in Millions	Dec. 31, 2020USD ($)
Domestic
Operating Loss Carryforwards [Line Items]
Net operating loss	$ 4.7
Foreign
Operating Loss Carryforwards [Line Items]
Net operating loss	22.5
Operating loss carryforward subject to valuation allowance	22.4
Foreign | No expiry
Operating Loss Carryforwards [Line Items]
Net operating loss	6.6
Foreign | 2021
Operating Loss Carryforwards [Line Items]
Net operating loss	5.7
Foreign | 2022
Operating Loss Carryforwards [Line Items]
Net operating loss	5.5
Foreign | 2023
Operating Loss Carryforwards [Line Items]
Net operating loss	0.9
Foreign | 2024
Operating Loss Carryforwards [Line Items]
Net operating loss	1.7
Foreign | 2025
Operating Loss Carryforwards [Line Items]
Net operating loss	$ 2.1

INCOME TAXES (Unrecognized Tax

INCOME TAXES (Unrecognized Tax Benefits) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Contingency [Line Items]
Significant new tax position resulted in increase in prior year	$ 500	$ 0	$ 0
Significant new tax position resulted in increase in current year	800	0	$ 0
Tax positions for which significant change in unrecognized tax benefits is reasonably possible	0
Income Taxes Payable, Noncurrent
Income Tax Contingency [Line Items]
Unrecognized tax benefit	$ 3,300	$ 2,900

EARNINGS PER SHARE (Details)

EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended																12 Months Ended
	Dec. 31, 2020		Sep. 30, 2020		Jun. 30, 2020		Mar. 31, 2020		Dec. 31, 2019		Sep. 30, 2019		Jun. 30, 2019		Mar. 31, 2019		Dec. 31, 2020		Dec. 31, 2019		Dec. 31, 2018
Numerator for basic and diluted earnings per share:
Net income	$ 85,539		$ 89,432		$ 66,624		$ 85,565		$ 74,524		$ 67,002		$ 58,777		$ 60,754		$ 327,160		$ 261,057		$ 240,256
Numerator for basic and diluted earnings per share																	$ 327,160		$ 261,057		$ 240,256
Denominator:
Weighted average common shares for basic earnings per share																	55,727		54,719		53,623
Net effect of dilutive stock options, restricted stock units and restricted stock awards																	2,719		2,949		3,050
Weighted average common shares for diluted earnings per share																	58,446		57,668		56,673
Net Income per share:
Basic (in dollars per share)	$ 1.53	[1]	$ 1.60	[1]	$ 1.20	[1]	$ 1.55	[1]	$ 1.35	[2]	$ 1.22	[2]	$ 1.07	[2]	$ 1.12	[2]	$ 5.87	[1]	$ 4.77	[2]	$ 4.48
Diluted (in dollars per share)	$ 1.46	[1]	$ 1.53	[1]	$ 1.14	[1]	$ 1.47	[1]	$ 1.29	[2]	$ 1.16	[2]	$ 1.02	[2]	$ 1.06	[2]	$ 5.60	[1]	$ 4.53	[2]	$ 4.24
Anti-dilutive stock excluded from the calculation (in shares)																	40		120		139
[1]	Earnings per share amounts for each quarter may not necessarily total to the yearly earnings per share due to the weighting of shares outstanding on a quarterly and year to date basis.
[2]	Earnings per share amounts for each quarter may not necessarily total to the yearly earnings per share due to the weighting of shares outstanding on a quarterly and year to date basis.

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Building Acquisition Commitment) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020USD ($)
Office space purchase commitment | Ukraine
Other Commitments [Line Items]
Total commitment amount	$ 36.9

SEGMENT INFORMATION (Revenues f

SEGMENT INFORMATION (Revenues from External Customers and Operating Profit Before Unallocated Expenses) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Segment revenues	$ 723,493	$ 652,243	$ 632,383	$ 651,359	$ 632,775	$ 588,103	$ 551,587	$ 521,333	$ 2,659,478	$ 2,293,798	$ 1,842,912
Income from operations	$ 111,993	$ 96,396	$ 83,426	$ 87,509	$ 84,745	$ 80,565	$ 72,882	$ 64,658	379,324	302,850	245,764
Segments
Segment Reporting Information [Line Items]
Income from operations									503,909	425,967	349,099
North America Segment
Segment Reporting Information [Line Items]
Segment revenues									1,601,820	1,380,944	1,076,979
Income from operations									345,196	293,757	221,846
Europe Segment
Segment Reporting Information [Line Items]
Segment revenues									947,305	820,717	692,785
Income from operations									152,902	114,863	115,876
Russia Segment
Segment Reporting Information [Line Items]
Segment revenues									110,353	92,137	73,148
Income from operations									$ 5,811	$ 17,347	$ 11,377

SEGMENT INFORMATION (Major Cust

SEGMENT INFORMATION (Major Customers) (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segments | Revenue | Customer concentration risk
Revenue, Major Customer [Line Items]
Number of customers	0	0	0

SEGMENT INFORMATION (Reconcilia

SEGMENT INFORMATION (Reconciliation of Segment Operating Profit to Consolidated Income Before Provision for Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income from operations	$ 111,993	$ 96,396	$ 83,426	$ 87,509	$ 84,745	$ 80,565	$ 72,882	$ 64,658	$ 379,324	$ 302,850	$ 245,764
Stock-based compensation expense									75,238	72,036	59,188
Amortization of purchased intangibles									12,340	9,914	8,511
Interest and other income, net	(2,053)	1,672	1,817	2,386	1,950	2,509	1,190	3,076	3,822	8,725	3,522
Foreign exchange (loss)/gain	(7,920)	5,896	(9,167)	6,524	(1,898)	(3,105)	(3,562)	(3,484)	(4,667)	(12,049)	487
Income before provision for income taxes	$ 102,020	$ 103,964	$ 76,076	$ 96,419	$ 84,797	$ 79,969	$ 70,510	$ 64,250	378,479	299,526	249,773
Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income from operations									503,909	425,967	349,099
Unallocated costs
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Stock-based compensation expense									(75,238)	(72,036)	(59,188)
Amortization of purchased intangibles									(12,340)	(9,914)	(8,101)
Other acquisition-related expenses									(1,868)	(3,774)	(916)
Other unallocated costs									$ (35,139)	$ (37,393)	$ (35,130)

SEGMENT INFORMATION (Physical L

SEGMENT INFORMATION (Physical Locations and Values of Long-Lived Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Long-Lived Assets by Geographical Areas [Line Items]
Long-lived assets	$ 169,533	$ 165,259	$ 102,646
Belarus
Long-Lived Assets by Geographical Areas [Line Items]
Long-lived assets	73,988	75,984	50,085
Ukraine
Long-Lived Assets by Geographical Areas [Line Items]
Long-lived assets	30,980	24,652	8,433
United States
Long-Lived Assets by Geographical Areas [Line Items]
Long-lived assets	15,718	15,637	13,101
Russia
Long-Lived Assets by Geographical Areas [Line Items]
Long-lived assets	15,036	17,980	9,902
India
Long-Lived Assets by Geographical Areas [Line Items]
Long-lived assets	7,079	7,443	7,019
Poland
Long-Lived Assets by Geographical Areas [Line Items]
Long-lived assets	5,434	5,029	2,637
Hungary
Long-Lived Assets by Geographical Areas [Line Items]
Long-lived assets	5,365	5,201	3,168
Spain
Long-Lived Assets by Geographical Areas [Line Items]
Long-lived assets	2,799	1,106	875
China
Long-Lived Assets by Geographical Areas [Line Items]
Long-lived assets	2,722	3,036	2,651
Mexico
Long-Lived Assets by Geographical Areas [Line Items]
Long-lived assets	2,419	2,353	812
Other
Long-Lived Assets by Geographical Areas [Line Items]
Long-lived assets	$ 7,993	$ 6,838	$ 3,963

SEGMENT INFORMATION (Revenues b

SEGMENT INFORMATION (Revenues by Customer Location) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	$ 723,493	$ 652,243	$ 632,383	$ 651,359	$ 632,775	$ 588,103	$ 551,587	$ 521,333	$ 2,659,478	$ 2,293,798	$ 1,842,912
United States
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									1,523,731	1,321,662	1,029,327
United Kingdom
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									331,217	290,039	200,918
Switzerland
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									203,391	152,710	144,398
Netherlands
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									114,678	88,488	70,274
Russia
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									104,846	89,941	71,181
Germany
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									84,902	82,441	80,787
Canada
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									68,416	68,304	69,836
Other locations
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									$ 228,297	$ 200,213	$ 176,191

ACCUMULATED OTHER COMPREHENSI_3

ACCUMULATED OTHER COMPREHENSIVE LOSS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020		Dec. 31, 2019	Dec. 31, 2018
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other comprehensive loss after reclassification and tax	$ 5,862		$ 10,140	$ (23,891)
AOCI Attributable to Parent [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning of period	(31,374)		(41,514)
Other comprehensive loss after reclassification and tax	5,862		10,140	(23,891)
Balance, end of period	(25,512)		(31,374)	(41,514)
Foreign currency translation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning of period	(32,666)		(38,961)	(17,623)
Other comprehensive loss before reclassifications and tax	5,802		7,912	(25,097)
Income tax (expense)/benefit	(1,304)		(1,617)	3,759
Other comprehensive loss after reclassification and tax	4,498		6,295	(21,338)
Balance, end of period	(28,168)		(32,666)	(38,961)
Cash flow hedging instruments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning of period	1,292		(2,553)	0
Other comprehensive loss before reclassifications and tax	8,076		2,933	867
Income tax (expense)/benefit	(695)		(1,116)	741
Other comprehensive loss after reclassification and tax	2,350		3,845	(2,553)
Balance, end of period	3,642	[1]	1,292	(2,553)
Cash flow hedging instruments | Cost of revenues (exclusive of depreciation and amortization)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Net (loss)/gain reclassified into Cost of revenues (exclusive of depreciation and amortization)	(5,031)		2,028	(4,161)
Defined benefit plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance, beginning of period	0		0	0
Other comprehensive loss before reclassifications and tax	(1,275)		0	0
Income tax (expense)/benefit	289		0	0
Other comprehensive loss after reclassification and tax	(986)		0	0
Balance, end of period	$ (986)		$ 0	$ 0
[1]	As of December 31, 2020, the ending balance of net unrealized gains related to derivatives designated as cash flow hedges is expected to be reclassified into Cost of revenues (exclusive of depreciation and amortization) in the next twelve months.

QUARTERLY FINANCIAL DATA (UNA_3

QUARTERLY FINANCIAL DATA (UNAUDITED) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended																12 Months Ended
	Dec. 31, 2020		Sep. 30, 2020		Jun. 30, 2020		Mar. 31, 2020		Dec. 31, 2019		Sep. 30, 2019		Jun. 30, 2019		Mar. 31, 2019		Dec. 31, 2020		Dec. 31, 2019		Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 723,493		$ 652,243		$ 632,383		$ 651,359		$ 632,775		$ 588,103		$ 551,587		$ 521,333		$ 2,659,478		$ 2,293,798		$ 1,842,912
Cost of revenues (exclusive of depreciation and amortization)	465,792		423,388		419,540		423,802		410,069		377,525		355,915		344,689		1,732,522		1,488,198		1,186,921
Selling, general and administrative expenses	128,929		116,530		114,191		125,108		124,999		118,886		111,762		101,786		484,758		457,433		373,587
Depreciation and amortization expense	16,779		15,929		15,226		14,940		12,962		11,127		11,028		10,200		62,874		45,317		36,640
Income from operations	111,993		96,396		83,426		87,509		84,745		80,565		72,882		64,658		379,324		302,850		245,764
Interest and other income, net	(2,053)		1,672		1,817		2,386		1,950		2,509		1,190		3,076		3,822		8,725		3,522
Foreign exchange (loss)/gain	(7,920)		5,896		(9,167)		6,524		(1,898)		(3,105)		(3,562)		(3,484)		(4,667)		(12,049)		487
Income before provision for income taxes	102,020		103,964		76,076		96,419		84,797		79,969		70,510		64,250		378,479		299,526		249,773
Provision for/(benefit from) income taxes	16,481		14,532		9,452		10,854		10,273		12,967		11,733		3,496		51,319		38,469		9,517
Net income	85,539		89,432		66,624		85,565		74,524		67,002		58,777		60,754		327,160		261,057		240,256
Comprehensive income	$ 110,699		$ 89,133		$ 85,512		$ 47,678		$ 86,741		$ 54,725		$ 62,934		$ 66,797		$ 333,022		$ 271,197		$ 216,365
Basic net income per share	$ 1.53	[1]	$ 1.60	[1]	$ 1.20	[1]	$ 1.55	[1]	$ 1.35	[2]	$ 1.22	[2]	$ 1.07	[2]	$ 1.12	[2]	$ 5.87	[1]	$ 4.77	[2]	$ 4.48
Diluted net income per share	$ 1.46	[1]	$ 1.53	[1]	$ 1.14	[1]	$ 1.47	[1]	$ 1.29	[2]	$ 1.16	[2]	$ 1.02	[2]	$ 1.06	[2]	$ 5.60	[1]	$ 4.53	[2]	$ 4.24
[1]	Earnings per share amounts for each quarter may not necessarily total to the yearly earnings per share due to the weighting of shares outstanding on a quarterly and year to date basis.
[2]	Earnings per share amounts for each quarter may not necessarily total to the yearly earnings per share due to the weighting of shares outstanding on a quarterly and year to date basis.

VALUATION AND QUALIFYING ACCO_3

VALUATION AND QUALIFYING ACCOUNTS (Valuation and Qualifying Accounts) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Allowance for doubtful accounts for trade receivables and contract assets
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	$ 3,210	$ 1,557	$ 1,186
Additions	3,282	2,072	2,722
Deductions/ Write offs	(1,606)	(419)	(2,351)
Balance at End of Year	4,886	3,210	1,557
Valuation allowance on deferred tax assets
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	3,877	3,189	924
Additions	1,608	688	2,265
Deductions/ Write offs	0	0	0
Balance at End of Year	$ 5,485	$ 3,877	$ 3,189