Convertible Senior Notes - Schedule of Components of Convertible Senior Notes (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Nov. 30, 2017
0.125% Convertible Senior Notes Due 2024
Liability component:
Principal	$ 450,000
Less: debt discount, net of amortization	(98,942)
Net carrying amount	351,058
Equity component	86,133
1.50% Convertible Senior Notes Due 2022
Liability component:
Principal	92,000	$ 115,000	$ 115,000
Less: debt discount, net of amortization	(12,776)	(20,903)
Net carrying amount	79,224	94,097
Equity component	$ (14,555)	$ 22,094

Debt instrument unamortized discount.

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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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