Acquisitions - Summary of Components of Purchase Consideration Transferred and Preliminary Allocation of Assets Acquired and Liabilities Assumed (Detail) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Jan. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Purchase Price
Cash and stock issued at closing		$ 5,850	$ 33,939	$ 34,513
Allocations
Goodwill		560,332	557,914	$ 515,321
HVS
Purchase Price
Cash and stock issued at closing	$ 6,249
Contingent consideration	3,590
Total	9,839	9,800
Allocations
Goodwill	6,294	$ 6,300
Other intangible assets, net	2,700
Receivables, net	796
Fixed Assets, net	134
Other assets	29
Accounts payable, accrued expenses and other liabilities	(114)
Net assets acquired	$ 9,839
2019 Acquisitions
Purchase Price
Cash and stock issued at closing			38,826
Contingent consideration			18,067
Total			56,893
Allocations
Cash and cash equivalents			1,391
Goodwill			43,804
Other intangible assets, net			9,641
Receivables, net			7,540
Other assets			614
Accounts payable, accrued expenses and other liabilities			(3,972)
Accrued compensation			(2,125)
Net assets acquired			$ 56,893