Convertible Senior Notes - Summary of Fair Value and Carrying Value of Convertible Senior Notes (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
0.125% Convertible Senior Notes Due 2024 | Fair Value
Debt Instrument [Line Items]
Convertible senior notes	$ 450,414
0.125% Convertible Senior Notes Due 2024 | Carrying Value
Debt Instrument [Line Items]
Convertible senior notes	351,058
1.50% Convertible Senior Notes Due 2022 | Fair Value
Debt Instrument [Line Items]
Convertible senior notes	215,801	$ 189,802
1.50% Convertible Senior Notes Due 2022 | Carrying Value
Debt Instrument [Line Items]
Convertible senior notes	$ 79,224	$ 94,097