CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Statement [Abstract]
Revenues	$ 3,758,144	$ 2,659,478	$ 2,293,798
Operating expenses:
Cost of revenues (exclusive of depreciation and amortization)	2,483,697	1,732,522	1,488,198
Selling, general and administrative expenses	648,736	484,758	457,433
Depreciation and amortization expense	83,395	62,874	45,317
Income from operations	542,316	379,324	302,850
Interest and other (loss)/income, net	(1,727)	3,822	8,725
Foreign exchange loss	(7,197)	(4,667)	(12,049)
Income before provision for income taxes	533,392	378,479	299,526
Provision for income taxes	51,740	51,319	38,469
Net income	$ 481,652	$ 327,160	$ 261,057
Net income per share:
Basic (in dollars per share)	$ 8.52	$ 5.87	$ 4.77
Diluted (in dollars per share)	$ 8.15	$ 5.60	$ 4.53
Shares used in calculation of net income per share:
Basic (in shares)	56,511	55,727	54,719
Diluted (in shares)	59,064	58,446	57,668