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Goodwill and Intangible Assets - Schedule of changes in goodwill by reporting unit (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Goodwill [Roll Forward]
Opening balance	$ 1,695,688	$ 1,574,466
Goodwill relating to acquisitions consummated during the period	44,216	123,595
Impact of measurement period adjustments	1,205	(5,653)
Effect of exchange rate fluctuations	(10,082)	3,280
Closing balance	1,731,027	1,695,688
BCMI
Goodwill [Roll Forward]
Opening balance	420,172	417,213
Goodwill relating to acquisitions consummated during the period	4,167	2,559
Impact of measurement period adjustments	35	(542)
Effect of exchange rate fluctuations	(3,117)	942
Closing balance	421,257	420,172
CGRLH
Goodwill [Roll Forward]
Opening balance	607,574	555,130
Goodwill relating to acquisitions consummated during the period	7,032	52,612
Impact of measurement period adjustments	309	(1,372)
Effect of exchange rate fluctuations	(3,795)	1,204
Closing balance	611,120	607,574
HMS
Goodwill [Roll Forward]
Opening balance	667,942	602,123
Goodwill relating to acquisitions consummated during the period	33,017	68,424
Impact of measurement period adjustments	861	(3,739)
Effect of exchange rate fluctuations	(3,170)	1,134
Closing balance	$ 698,650	$ 667,942

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