Debt - Net Carrying Amount of Liability Component of Debt Discount (Details) - Convertible Notes Payable - USD ($)	Mar. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Face amount of the Notes	$ 167,110,000	$ 160,090,000
Less unamortized discounts and debt issuance costs	(19,621,000)	(20,519,000)
Total net carrying value, non-current	147,489,000	139,571,000
Revolving Credit Facility
Debt Instrument [Line Items]
Face amount of the Notes	20,000,000	15,000,000
Senior Notes, due December 2019
Debt Instrument [Line Items]
Face amount of the Notes	13,022,000	15,702,000
Less unamortized discounts and debt issuance costs	(808,000)	(1,291,000)
Total net carrying value	12,214,000	14,411,000
Senior Notes, due May 2023
Debt Instrument [Line Items]
Face amount of the Notes	75,090,000	75,090,000
Senior Notes, due February 2023
Debt Instrument [Line Items]
Face amount of the Notes	$ 72,020,000	$ 70,000,000

Including the current and noncurrent portions, carrying amount of debt identified as being convertible into another form of financial instrument (typically the entity's common stock) as of the balance sheet date, which originally required full repayment more than twelve months after issuance or greater than the normal operating cycle of the company.

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- Definition

The portion of the carrying value of long-term convertible debt as of the balance sheet date that is scheduled to be repaid within one year or in the normal operating cycle if longer. Convertible debt is a financial instrument which can be exchanged for a specified amount of another security, typically the entity's common stock, at the option of the issuer or the holder.

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

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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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Amount of unamortized debt discount (premium) and debt issuance costs.

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