Debt - Summary of Interest Expense on Convertible Debt (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Schedule Of Interest Expenses [Line Items]
Total interest expense on convertible debt	$ 9,597	$ 2,937	$ 24,560	$ 16,530
Convertible Senior Notes
Schedule Of Interest Expenses [Line Items]
Accretion of discount on convertible notes	4,696	4,005	13,201	11,860
Coupon interest expense	4,255	2,271	9,443	6,681
Amortization of debt issuance costs	535	508	1,565	1,522
Total interest expense on convertible debt	$ 9,486	$ 6,784	$ 24,209	$ 20,063