Equity and Changes in Equity During Period (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Class Of Stock [Line Items]
Balance at beginning of period				$ 1,117,816
Net income		$ 22,745	$ 12,988	83,631	$ 45,457
Currency translation		(92)	$ 299	(392)	$ 749
Stock-based compensation				42,755
Shares repurchased and retired to satisfy tax withholding upon vesting				(28,238)
Stock option exercises, net of withholdings and other				13,010
Stock-based compensation, assumed ISO awards				2,594
Balance at end of period		1,432,058		1,432,058
Common stock | Accredited Investor
Class Of Stock [Line Items]
Issuance of common stock				200,000
ASC Topic 606
Class Of Stock [Line Items]
Cumulative effect of change in accounting principle	[1]	$ 882		$ 882

[1] See Note 2, Significant Accounting Policies, for additional details related to the impact of the adoption of ASC Topic 606 during the nine months ended September 30, 2018