Income Taxes - Summary of Components of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred Tax Assets, Gross [Abstract]
Allowance for doubtful accounts	$ 11,792	$ 11,279
Accrued vacation and bonus	23,545	23,896
Deferred rent	9,016	8,491
Share-based compensation	11,837	15,108
Notes receivable from employees	12,993	12,879
State net operating loss carryforward	3,510	3,586
Foreign net operating loss carryforward	9,857	12,075
Federal tax credit and capital loss carryforward	9,470	7,403
Deferred compensation	1,801	2,688
Other, net	1,129	7,159
Total deferred tax assets	94,950	104,564
Deferred tax liabilities
Revenue recognition	(5,087)	(7,227)
Property, equipment and capitalized software	(6,652)	(2,308)
Equity debt discount	(11,014)	0
Goodwill and other intangible asset amortization	(199,964)	(190,638)
Total deferred tax liabilities	(222,717)	(200,173)
Foreign withholding tax	(413)	(1,035)
Valuation allowance	(21,929)	(21,621)
Net deferred tax liabilities	$ (150,109)	$ (118,265)