Convertible Senior Notes - Schedule of Components of Convertible Senior Notes (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019	Nov. 30, 2017
0.125% Convertible Senior Notes Due 2024
Liability component:
Principal	$ 450,000	$ 450,000
Less: debt discount, net of amortization	(85,549)	(98,942)
Net carrying amount	364,451	351,058
Equity component	86,133	86,133
1.50% Convertible Senior Notes Due 2022
Liability component:
Principal	90,992	92,000	$ 115,000
Less: debt discount, net of amortization	(9,528)	(12,776)
Net carrying amount	81,464	79,224
Equity component	$ (19,167)	$ (14,555)

Debt instrument unamortized discount.

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- Definition

Including the current and noncurrent portions, carrying value as of the balance sheet date of a written promise to pay a note, initially due after one year or beyond the operating cycle if longer, which can be exchanged for a specified amount of one or more securities (typically common stock), at the option of the issuer or the holder.

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- Definition

The carrying amount of the equity component of convertible debt which may be settled in cash upon conversion.

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- Definition

Face (par) amount of debt instrument at time of issuance.

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- Definition

Amount, after accumulated amortization, of debt discount.

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