Stock-based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total share-based compensation expense	$ 10,630	$ 15,440	$ 19,537	$ 33,578
Employee Stock Option | Selling, general and administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total share-based compensation expense	963	1,952	1,883	4,938
Employee Stock Option | Research and development
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total share-based compensation expense	731	1,882	1,572	4,215
Restricted Stock Units | Selling, general and administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total share-based compensation expense	3,767	5,500	7,539	12,389
Restricted Stock Units | Research and development
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total share-based compensation expense	$ 5,169	$ 6,106	$ 8,543	$ 12,036