Debt - Summary of Convertible Debt (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Convertible Notes	$ 1,500,000
Short-term convertible debt, net	370,100	$ 361,882	[1]
Convertible Notes, net of unamortized discount and deferred offering costs	1,073,202	486,238	[1]
Total convertible debt, net	1,443,302	848,120
Total fair value of fixed rate convertible debt	$ 1,805,649	$ 933,309
1.25% Senior Subordinated Convertible Notes Due in May 2027
Debt Instrument [Line Items]
Convertible notes stated rate	1.25%	1.25%
Convertible Notes	$ 600,000	$ 0
Convertible debt, unamortized discount	(13,269)	0
Convertible debt, Unamortized deferred offering costs	(717)	0
Convertible Notes, net of unamortized discount and deferred offering costs	586,014	0
Total fair value of fixed rate convertible debt	$ 702,882	$ 0
0.599% Senior Subordinated Convertible Notes Due in August 2024
Debt Instrument [Line Items]
Convertible notes stated rate	0.599%	0.599%
Convertible Notes	$ 495,000	$ 495,000
Convertible debt, unamortized discount	(5,825)	(6,533)
Convertible debt, Unamortized deferred offering costs	(1,987)	(2,229)
Convertible Notes, net of unamortized discount and deferred offering costs	487,188	486,238
Total fair value of fixed rate convertible debt	$ 609,216	$ 512,582
1.50% Senior Subordinated Convertible Notes Due in October 2020
Debt Instrument [Line Items]
Convertible notes stated rate	1.50%	1.50%
Convertible Notes	$ 374,993	$ 374,993
Convertible debt, unamortized discount	(4,512)	(12,078)
Convertible debt, Unamortized deferred offering costs	(381)	(1,033)
Short-term convertible debt, net	370,100	361,882
Total fair value of fixed rate convertible debt	$ 493,551	$ 420,727

[1] December 31, 2019 balances were derived from the audited Consolidated Financial Statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019, filed with the SEC on February 27, 2020.