Convertible Senior Notes - Additional Information (Detail) - USD ($) $ in Thousands		3 Months Ended	9 Months Ended
	Jul. 19, 2019	Sep. 30, 2021	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Jul. 31, 2019
Debt Instrument [Line Items]
Accretion of the debt discount			$ 8,592	$ 8,175
Repayment of convertible debt			9
Repayment of convertible debt			$ 9
0.375% Convertible Senior Notes due 2024
Debt Instrument [Line Items]
Notes issued	$ 287,500					$ 287,500
Notes, interest rate	0.375%
Proceeds from issuance of convertible senior notes, net of costs	$ 278,500
Interest repayment terms			Interest is payable semi-annually in arrears on January 15 and July 15 of each year, beginning on January 15, 2020.
Notes, due date	Jul. 15, 2024
Contractual coupon interest		$ 300	$ 800
Accretion of the debt discount		2,500	7,500
Amortization of the debt issuance costs		$ 400	$ 1,100
Effective interest rate on the Notes		5.10%	5.10%
Notes, carrying value		$ 252,300	$ 252,300		$ 243,700
Fair value of the note		732,900	732,900		$ 501,000
Additional Notes issued	$ 37,500
Debt instrument amount convertible into equity		6,000	6,000
Loss on conversion of debt included in other expenses		$ 1,000	$ 6,000
Excess common stock price percentage		130.00%