REVENUES (Schedule of Disaggregation of Revenues) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disaggregation of Revenue [Line Items]
Revenues	$ 4,690,540	$ 4,824,698	$ 3,758,144
Revenues from performance obligations satisfied in previous period	5,800	7,500	18,700
Transferred over time
Disaggregation of Revenue [Line Items]
Revenues	4,674,989	4,810,148	3,747,565
Transferred at a point of time
Disaggregation of Revenue [Line Items]
Revenues	15,551	14,550	10,579
Time-and-material
Disaggregation of Revenue [Line Items]
Revenues	4,082,503	4,239,580	3,209,747
Fixed-price
Disaggregation of Revenue [Line Items]
Revenues	579,230	560,467	529,396
Licensing and other revenues
Disaggregation of Revenue [Line Items]
Revenues	28,807	24,651	19,001
Travel & Consumer
Disaggregation of Revenue [Line Items]
Revenues	1,072,950	1,092,224	741,128
Financial Services
Disaggregation of Revenue [Line Items]
Revenues	1,018,433	1,026,686	848,370
Business Information & Media
Disaggregation of Revenue [Line Items]
Revenues	753,981	809,952	666,941
Software & Hi-Tech
Disaggregation of Revenue [Line Items]
Revenues	707,720	793,261	664,597
Life Sciences & Healthcare
Disaggregation of Revenue [Line Items]
Revenues	489,914	507,367	391,309
Emerging Verticals
Disaggregation of Revenue [Line Items]
Revenues	647,542	595,208	445,799
North America
Disaggregation of Revenue [Line Items]
Revenues	2,765,022	2,898,554	2,242,248
North America | Transferred over time
Disaggregation of Revenue [Line Items]
Revenues	2,751,937	2,888,342	2,232,308
North America | Transferred at a point of time
Disaggregation of Revenue [Line Items]
Revenues	13,085	10,212	9,940
North America | Time-and-material
Disaggregation of Revenue [Line Items]
Revenues	2,457,545	2,615,213	1,981,696
North America | Fixed-price
Disaggregation of Revenue [Line Items]
Revenues	283,183	263,603	244,249
North America | Licensing and other revenues
Disaggregation of Revenue [Line Items]
Revenues	24,294	19,738	16,303
North America | Travel & Consumer
Disaggregation of Revenue [Line Items]
Revenues	472,350	505,227	359,306
North America | Financial Services
Disaggregation of Revenue [Line Items]
Revenues	538,837	522,970	361,611
North America | Business Information & Media
Disaggregation of Revenue [Line Items]
Revenues	429,800	467,664	389,613
North America | Software & Hi-Tech
Disaggregation of Revenue [Line Items]
Revenues	552,492	655,122	559,707
North America | Life Sciences & Healthcare
Disaggregation of Revenue [Line Items]
Revenues	429,245	454,102	340,706
North America | Emerging Verticals
Disaggregation of Revenue [Line Items]
Revenues	342,298	293,469	231,305
Europe
Disaggregation of Revenue [Line Items]
Revenues	1,909,443	1,853,056	1,350,484
Europe | Transferred over time
Disaggregation of Revenue [Line Items]
Revenues	1,907,010	1,849,011	1,349,956
Europe | Transferred at a point of time
Disaggregation of Revenue [Line Items]
Revenues	2,433	4,045	528
Europe | Time-and-material
Disaggregation of Revenue [Line Items]
Revenues	1,613,790	1,578,786	1,145,606
Europe | Fixed-price
Disaggregation of Revenue [Line Items]
Revenues	291,174	269,669	202,436
Europe | Licensing and other revenues
Disaggregation of Revenue [Line Items]
Revenues	4,479	4,601	2,442
Europe | Travel & Consumer
Disaggregation of Revenue [Line Items]
Revenues	596,830	571,437	354,041
Europe | Financial Services
Disaggregation of Revenue [Line Items]
Revenues	472,146	460,858	372,394
Europe | Business Information & Media
Disaggregation of Revenue [Line Items]
Revenues	323,985	341,344	275,502
Europe | Software & Hi-Tech
Disaggregation of Revenue [Line Items]
Revenues	153,683	136,273	102,270
Europe | Life Sciences & Healthcare
Disaggregation of Revenue [Line Items]
Revenues	60,549	52,465	49,900
Europe | Emerging Verticals
Disaggregation of Revenue [Line Items]
Revenues	302,250	290,679	196,377
Russia
Disaggregation of Revenue [Line Items]
Revenues	16,075	73,088	165,412
Russia | Transferred over time
Disaggregation of Revenue [Line Items]
Revenues	16,042	72,795	165,301
Russia | Transferred at a point of time
Disaggregation of Revenue [Line Items]
Revenues	33	293	111
Russia | Time-and-material
Disaggregation of Revenue [Line Items]
Revenues	11,168	45,581	82,445
Russia | Fixed-price
Disaggregation of Revenue [Line Items]
Revenues	4,873	27,195	82,711
Russia | Licensing and other revenues
Disaggregation of Revenue [Line Items]
Revenues	34	312	256
Russia | Travel & Consumer
Disaggregation of Revenue [Line Items]
Revenues	3,770	15,560	27,781
Russia | Financial Services
Disaggregation of Revenue [Line Items]
Revenues	7,450	42,858	114,365
Russia | Business Information & Media
Disaggregation of Revenue [Line Items]
Revenues	196	944	1,826
Russia | Software & Hi-Tech
Disaggregation of Revenue [Line Items]
Revenues	1,545	1,866	2,620
Russia | Life Sciences & Healthcare
Disaggregation of Revenue [Line Items]
Revenues	120	800	703
Russia | Emerging Verticals
Disaggregation of Revenue [Line Items]
Revenues	2,994	11,060	18,117
Americas
Disaggregation of Revenue [Line Items]
Revenues	2,742,662	2,887,204	2,226,830
Americas | North America
Disaggregation of Revenue [Line Items]
Revenues	2,645,174	2,792,156	2,145,163
Americas | Europe
Disaggregation of Revenue [Line Items]
Revenues	96,857	92,244	77,351
Americas | Russia
Disaggregation of Revenue [Line Items]
Revenues	631	2,804	4,316
EMEA
Disaggregation of Revenue [Line Items]
Revenues	1,822,782	1,737,919	1,259,717
EMEA | North America
Disaggregation of Revenue [Line Items]
Revenues	116,054	95,706	87,121
EMEA | Europe
Disaggregation of Revenue [Line Items]
Revenues	1,706,728	1,642,114	1,172,267
EMEA | Russia
Disaggregation of Revenue [Line Items]
Revenues	0	99	329
APAC
Disaggregation of Revenue [Line Items]
Revenues	102,138	120,370	103,559
APAC | North America
Disaggregation of Revenue [Line Items]
Revenues	3,248	3,837	3,224
APAC | Europe
Disaggregation of Revenue [Line Items]
Revenues	98,890	116,533	100,335
APAC | Russia
Disaggregation of Revenue [Line Items]
Revenues	0	0	0
CEE
Disaggregation of Revenue [Line Items]
Revenues	22,958	79,205	168,038
CEE | North America
Disaggregation of Revenue [Line Items]
Revenues	546	6,855	6,740
CEE | Europe
Disaggregation of Revenue [Line Items]
Revenues	6,968	2,165	531
CEE | Russia
Disaggregation of Revenue [Line Items]
Revenues	$ 15,444	$ 70,185	$ 160,767