REVENUES (Schedule of Disaggregation of Revenues) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Disaggregation of Revenue [Line Items]
Revenues	$ 4,824,698	$ 3,758,144	$ 2,659,478
Revenues from performance obligations satisfied in previous period	7,500	18,700	5,000
Transferred over time
Disaggregation of Revenue [Line Items]
Revenues	4,810,148	3,747,565	2,650,991
Transferred at a point of time
Disaggregation of Revenue [Line Items]
Revenues	14,550	10,579	8,487
Time-and-material
Disaggregation of Revenue [Line Items]
Revenues	4,239,580	3,209,747	2,291,004
Fixed-price
Disaggregation of Revenue [Line Items]
Revenues	560,467	529,396	352,012
Licensing and other revenues
Disaggregation of Revenue [Line Items]
Revenues	24,651	19,001	16,462
Travel & Consumer
Disaggregation of Revenue [Line Items]
Revenues	1,092,224	741,128	458,789
Financial Services
Disaggregation of Revenue [Line Items]
Revenues	1,026,686	848,370	555,235
Business Information & Media
Disaggregation of Revenue [Line Items]
Revenues	809,952	666,941	560,680
Software & Hi-Tech
Disaggregation of Revenue [Line Items]
Revenues	793,261	664,597	496,813
Life Sciences & Healthcare
Disaggregation of Revenue [Line Items]
Revenues	507,367	391,309	296,313
Emerging Verticals
Disaggregation of Revenue [Line Items]
Revenues	595,208	445,799	291,648
North America
Disaggregation of Revenue [Line Items]
Revenues	2,898,554	2,242,248	1,601,820
North America | Transferred over time
Disaggregation of Revenue [Line Items]
Revenues	2,888,342	2,232,308	1,595,786
North America | Transferred at a point of time
Disaggregation of Revenue [Line Items]
Revenues	10,212	9,940	6,034
North America | Time-and-material
Disaggregation of Revenue [Line Items]
Revenues	2,615,213	1,981,696	1,440,635
North America | Fixed-price
Disaggregation of Revenue [Line Items]
Revenues	263,603	244,249	151,769
North America | Licensing and other revenues
Disaggregation of Revenue [Line Items]
Revenues	19,738	16,303	9,416
North America | Travel & Consumer
Disaggregation of Revenue [Line Items]
Revenues	505,227	359,306	221,977
North America | Financial Services
Disaggregation of Revenue [Line Items]
Revenues	522,970	361,611	199,594
North America | Business Information & Media
Disaggregation of Revenue [Line Items]
Revenues	467,664	389,613	334,063
North America | Software & Hi-Tech
Disaggregation of Revenue [Line Items]
Revenues	655,122	559,707	419,895
North America | Life Sciences & Healthcare
Disaggregation of Revenue [Line Items]
Revenues	454,102	340,706	260,518
North America | Emerging Verticals
Disaggregation of Revenue [Line Items]
Revenues	293,469	231,305	165,773
Europe
Disaggregation of Revenue [Line Items]
Revenues	1,853,056	1,350,484	947,305
Europe | Transferred over time
Disaggregation of Revenue [Line Items]
Revenues	1,849,011	1,349,956	946,379
Europe | Transferred at a point of time
Disaggregation of Revenue [Line Items]
Revenues	4,045	528	926
Europe | Time-and-material
Disaggregation of Revenue [Line Items]
Revenues	1,578,786	1,145,606	790,203
Europe | Fixed-price
Disaggregation of Revenue [Line Items]
Revenues	269,669	202,436	151,718
Europe | Licensing and other revenues
Disaggregation of Revenue [Line Items]
Revenues	4,601	2,442	5,384
Europe | Travel & Consumer
Disaggregation of Revenue [Line Items]
Revenues	571,437	354,041	220,448
Europe | Financial Services
Disaggregation of Revenue [Line Items]
Revenues	460,858	372,394	278,355
Europe | Business Information & Media
Disaggregation of Revenue [Line Items]
Revenues	341,344	275,502	224,922
Europe | Software & Hi-Tech
Disaggregation of Revenue [Line Items]
Revenues	136,273	102,270	73,288
Europe | Life Sciences & Healthcare
Disaggregation of Revenue [Line Items]
Revenues	52,465	49,900	35,347
Europe | Emerging Verticals
Disaggregation of Revenue [Line Items]
Revenues	290,679	196,377	114,945
Russia
Disaggregation of Revenue [Line Items]
Revenues	73,088	165,412	110,353
Russia | Transferred over time
Disaggregation of Revenue [Line Items]
Revenues	72,795	165,301	108,826
Russia | Transferred at a point of time
Disaggregation of Revenue [Line Items]
Revenues	293	111	1,527
Russia | Time-and-material
Disaggregation of Revenue [Line Items]
Revenues	45,581	82,445	60,166
Russia | Fixed-price
Disaggregation of Revenue [Line Items]
Revenues	27,195	82,711	48,525
Russia | Licensing and other revenues
Disaggregation of Revenue [Line Items]
Revenues	312	256	1,662
Russia | Travel & Consumer
Disaggregation of Revenue [Line Items]
Revenues	15,560	27,781	16,364
Russia | Financial Services
Disaggregation of Revenue [Line Items]
Revenues	42,858	114,365	77,286
Russia | Business Information & Media
Disaggregation of Revenue [Line Items]
Revenues	944	1,826	1,695
Russia | Software & Hi-Tech
Disaggregation of Revenue [Line Items]
Revenues	1,866	2,620	3,630
Russia | Life Sciences & Healthcare
Disaggregation of Revenue [Line Items]
Revenues	800	703	448
Russia | Emerging Verticals
Disaggregation of Revenue [Line Items]
Revenues	11,060	18,117	10,930
Americas
Disaggregation of Revenue [Line Items]
Revenues	2,887,204	2,226,830	1,595,136
Americas | North America
Disaggregation of Revenue [Line Items]
Revenues	2,792,156	2,145,163	1,546,093
Americas | Europe
Disaggregation of Revenue [Line Items]
Revenues	92,244	77,351	45,553
Americas | Russia
Disaggregation of Revenue [Line Items]
Revenues	2,804	4,316	3,490
EMEA
Disaggregation of Revenue [Line Items]
Revenues	1,737,919	1,259,717	879,842
EMEA | North America
Disaggregation of Revenue [Line Items]
Revenues	95,706	87,121	45,733
EMEA | Europe
Disaggregation of Revenue [Line Items]
Revenues	1,642,114	1,172,267	834,033
EMEA | Russia
Disaggregation of Revenue [Line Items]
Revenues	99	329	76
APAC
Disaggregation of Revenue [Line Items]
Revenues	120,370	103,559	69,798
APAC | North America
Disaggregation of Revenue [Line Items]
Revenues	3,837	3,224	2,177
APAC | Europe
Disaggregation of Revenue [Line Items]
Revenues	116,533	100,335	67,621
APAC | Russia
Disaggregation of Revenue [Line Items]
Revenues	0	0	0
CEE
Disaggregation of Revenue [Line Items]
Revenues	79,205	168,038	114,702
CEE | North America
Disaggregation of Revenue [Line Items]
Revenues	6,855	6,740	7,817
CEE | Europe
Disaggregation of Revenue [Line Items]
Revenues	2,165	531	98
CEE | Russia
Disaggregation of Revenue [Line Items]
Revenues	$ 70,185	$ 160,767	$ 106,787