Convertible Senior Notes - Net proceeds (Details) - USD ($) $ in Thousands		3 Months Ended
Mar. 08, 2018	Mar. 31, 2019	Mar. 31, 2018
Convertible Senior Notes
Less cost of related capped call and common stock forward			$ (43,500)
Net proceeds			$ 96,057
Convertible Senior Notes
Convertible Senior Notes
Interest rate (as a percent)			5.50%
Convertible Senior Notes
Principal amount	$ 100,000	$ 100,000	$ 100,000
Less initial purchasers' discount	(3,250)
Less cost of related capped call and common stock forward	(43,500)
Less other issuance costs	(894)	$ (1,700)
Net proceeds	$ 52,356

Discount cost incurred related to the issuance of the debt.

No definition available.

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- Definition

Other cost incurred related to the issuance of the debt.

+ References

No definition available.

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- Definition

Amount of cash outflow arising from the purchase of capped call and common stock forward.

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- Definition

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

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

The cash inflow during the period from additional borrowings in aggregate debt. Includes proceeds from short-term and long-term debt.

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