Acquisitions - Summary of Components of Purchase Consideration Transferred and Preliminary Allocation of Assets Acquired and Liabilities Assumed (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Assets
Goodwill	$ 557,914	$ 515,321	$ 477,532
2019 Acquisitions
Assets
Cash and cash equivalents	1,391
Goodwill	43,804
Receivables, net	7,540
Other intangible assets, net	9,641
Other assets	614
Total assets	62,990
Liabilities
Accounts payable, accrued expenses and other liabilities	3,972
Accrued compensation	2,125
Total liabilities	6,097
Net assets acquired	$ 56,893
2018 Acquisitions
Assets
Cash and cash equivalents		1,110
Goodwill		42,188
Receivables, net		1,276
Fixed Assets, net		4,677
Other intangible assets, net		50,731
Other assets		2,894
Total assets		102,876
Liabilities
Accounts payable, accrued expenses and other liabilities		15,937
Accrued compensation		26,765
Total liabilities		42,702
Net assets acquired		$ 60,174