Notes Receivable from Employees - Summary of Changes in Carrying Amount of Notes Receivable From Employees (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Loans and Leases Receivable, Related Parties [Roll Forward]
Notes receivable from employees — beginning	$ 123,796	$ 136,388
Notes granted	32,937	18,247
Repayments	(5,405)	(7,394)
Amortization expense	(36,418)	(26,821)
Cumulative translation adjustment and other	(1,211)	3,376
Notes receivable from employees — ending	$ 123,796	$ 136,388	$ 113,699	$ 123,796
Less: current portion			(29,228)	(25,691)
Notes receivable from employees, net of current portion			$ 84,471	$ 98,105