Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Statement [Abstract]
Revenues	$ 20,882,206	$ 17,073,903	$ 12,980,213
Cost of services	17,945,120	14,544,748	11,026,954
Gross profit	2,937,086	2,529,155	1,953,259
Equity in earnings of integral unconsolidated affiliates	41,609	52,466	44,061
Selling, general and administrative expenses	(1,555,137)	(1,336,711)	(1,155,956)
Amortization of intangible assets	(289,014)	(353,973)	(165,366)
Asset impairment charges	0	(14,457)	(5,743)
Change in fair value of contingent consideration liabilities	(6,568)	(4,422)	(6,734)
Operating income	1,127,976	872,058	663,521
Interest and other financing expenses	(186,913)	(124,363)	(68,899)
Interest income	10,830	2,606	3,194
Other income (expense), net	18,063	(46,415)	25,085
Income before income taxes	969,956	703,886	622,901
Provision for income taxes	219,267	192,243	130,918
Net income	750,689	511,643	491,983
Less: Net income attributable to non-controlling interests	6,000	20,454	6,027
Net income attributable to common stock	$ 744,689	$ 491,189	$ 485,956
Earnings per share attributable to common stock:
Basic (in dollars per share)	$ 5.13	$ 3.42	$ 3.45
Diluted (in dollars per share)	$ 5.00	$ 3.32	$ 3.34
Shares used in computing earnings per share:
Weighted average basic shares outstanding (in shares)	145,222	143,488	140,824
Weighted average diluted shares outstanding (in shares)	148,823	147,992	145,373