Debt - Summary of Interest Expense on Convertible Debt (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Schedule Of Interest Expenses [Line Items]
Total interest expense on convertible debt	$ 8,048	$ 6,866	$ 14,963	$ 13,593
Convertible Senior Notes
Schedule Of Interest Expenses [Line Items]
Accretion of discount on convertible notes	4,395	3,953	8,505	7,855
Coupon interest expense	3,016	2,254	5,188	4,411
Amortization of debt issuance costs	522	508	1,030	1,015
Total interest expense on convertible debt	$ 7,933	$ 6,715	$ 14,723	$ 13,281