Stock-Based Compensation - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended		9 Months Ended
	Mar. 31, 2019	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted average grant date fair value of options granted, per share				$ 4.71	$ 5.02
Grant date fair values of options vested				$ 11,400,000	$ 4,300,000
Aggregate intrinsic values of options exercised				7,800,000	11,600,000
Unrecognized compensation cost		$ 29,000,000		$ 29,000,000
Weighted average period for recognition of compensation costs				2 years 10 months 24 days
Total payments for employees’ tax obligations				$ 2,410,000	0
RSUs Granted				708,144
Stock based compensation expenses		4,910,000	$ 7,179,000	$ 14,369,000	10,052,000
Stock-based compensation expense capitalized		0	$ 0	$ 0	$ 0
Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted average period for recognition of compensation costs				1 year 10 months 24 days
Total grant date fair value of RSUs				$ 5,500,000
Total fair value of RSUs vested				$ 5,900,000
Total shares withheld of RSUs				300,000
Total payments for employees’ tax obligations				$ 2,400,000
RSUs Granted					1,800,000
Stock based compensation expenses					$ 1,200,000
Unrecognized stock based compensation cost		$ 12,700,000		$ 12,700,000
Shares expected to vest		1,617,702		1,617,702
Minimum | Employees | Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period	2 years
Maximum | Employees | Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period	3 years