SEGMENT INFORMATION (Reconciliation of Segment Operating Profit to Consolidated Income Before Provision for Income Taxes) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Segment revenues	$ 1,353,443	$ 1,146,597	$ 2,655,135	$ 2,312,062
Cost of revenues (exclusive of depreciation and amortization)	964,012	810,857	1,916,020	1,645,191
Selling, general and administrative expenses	231,681	194,058	450,598	392,511
Depreciation and amortization expense	31,274	21,121	62,711	43,267
Stock-based compensation expense	(38,558)	(35,684)	(87,014)	(80,475)
Income from operations	126,476	120,561	225,806	231,093
Interest and other income, net	3,519	12,036	9,333	27,078
Foreign exchange (loss)/gain	(6,227)	1,213	(16,954)	(706)
Income before provision for income taxes	123,768	133,810	218,185	257,465
Americas
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Segment revenues	801,433	691,199	1,581,718	1,384,119
Operating Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Segment revenues	1,353,443	1,146,597	2,655,135	2,312,062
Cost of revenues (exclusive of depreciation and amortization)	948,223	800,293	1,874,535	1,614,385
Selling, general and administrative expenses	181,527	155,483	356,561	310,850
Depreciation and amortization expense	13,437	15,300	27,218	31,498
Segment operating profit	210,256	175,521	396,821	355,329
Operating Segments | Americas
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Segment revenues	787,400	698,629	1,564,568	1,403,358
Cost of revenues (exclusive of depreciation and amortization)	544,768	476,917	1,095,617	962,406
Selling, general and administrative expenses	103,999	89,592	205,517	178,283
Depreciation and amortization expense	9,143	10,051	18,716	20,458
Segment operating profit	129,490	122,069	244,718	242,211
Operating Segments | Europe
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Segment revenues	566,043	447,968	1,090,567	908,704
Cost of revenues (exclusive of depreciation and amortization)	403,455	323,376	778,918	651,979
Selling, general and administrative expenses	77,528	65,891	151,044	132,567
Depreciation and amortization expense	4,294	5,249	8,502	11,040
Segment operating profit	80,766	53,452	152,103	113,118
Unallocated Amounts
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Stock-based compensation expense	(38,558)	(35,684)	(87,014)	(80,475)
Amortization of purchased intangibles	(17,836)	(5,821)	(35,492)	(11,770)
Other acquisition-related expenses	(299)	(473)	(875)	(1,696)
Other unallocated costs	(27,087)	(12,982)	(47,634)	(30,295)
Income from operations	$ 126,476	$ 120,561	$ 225,806	$ 231,093