GOODWILL (Goodwill Roll Forward) (Details) $ in Thousands	6 Months Ended
Jun. 30, 2020 USD ($)
Goodwill [Roll Forward]
Balance as of January 1, 2020	$ 195,043
Effect of net foreign currency exchange rate changes	(2,670)
Balance as of June 30, 2020	199,039
test IO
Goodwill [Roll Forward]
Purchase accounting adjustments	(226)
Other 2019 Acquisitions
Goodwill [Roll Forward]
Purchase accounting adjustments	599
2020 Acquisition
Goodwill [Roll Forward]
Acquisition	6,293
North America
Goodwill [Roll Forward]
Balance as of January 1, 2020	113,426
Effect of net foreign currency exchange rate changes	(177)
Balance as of June 30, 2020	120,778
North America \| test IO
Goodwill [Roll Forward]
Purchase accounting adjustments	863
North America \| Other 2019 Acquisitions
Goodwill [Roll Forward]
Purchase accounting adjustments	373
North America \| 2020 Acquisition
Goodwill [Roll Forward]
Acquisition	6,293
Europe
Goodwill [Roll Forward]
Balance as of January 1, 2020	80,873
Effect of net foreign currency exchange rate changes	(2,460)
Balance as of June 30, 2020	77,515
Europe \| test IO
Goodwill [Roll Forward]
Purchase accounting adjustments	(1,089)
Europe \| Other 2019 Acquisitions
Goodwill [Roll Forward]
Purchase accounting adjustments	191
Europe \| 2020 Acquisition
Goodwill [Roll Forward]
Acquisition	0
Russia
Goodwill [Roll Forward]
Balance as of January 1, 2020	744
Effect of net foreign currency exchange rate changes	(33)
Balance as of June 30, 2020	746
Russia \| test IO
Goodwill [Roll Forward]
Purchase accounting adjustments	0
Russia \| Other 2019 Acquisitions
Goodwill [Roll Forward]
Purchase accounting adjustments	35
Russia \| 2020 Acquisition
Goodwill [Roll Forward]
Acquisition	$ 0

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(10)(1))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=120320667&loc=SL49117168-202975

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=99380562&loc=d3e13770-109266

+ Details

Name:	us-gaap_Goodwill
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121556970&loc=d3e13816-109267

+ Details

Name:	us-gaap_GoodwillAcquiredDuringPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of foreign currency translation gain (loss) which increases (decreases) an asset representing future economic benefits from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=121556970&loc=d3e13816-109267

+ Details

Name:	us-gaap_GoodwillForeignCurrencyTranslationGainLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of increase (decrease) from adjustments after acquisition date under purchase accounting of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 25
-Paragraph 16
-URI http://asc.fasb.org/extlink&oid=116868678&loc=d3e961-128460

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=121556970&loc=d3e13816-109267

+ Details

Name:	us-gaap_GoodwillPurchaseAccountingAdjustments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

Name:	us-gaap_GoodwillRollForward
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_BusinessAcquisitionAxis=epam_TestIOGmbhMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=epam_Other2019AcquisitionsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=epam_A2020AcquisitionsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=epam_NorthAmericaSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=epam_EuropeSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=epam_RussiaSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: