Debt - Net Carrying Amount of Liability Component of Debt Discount (Details) - USD ($)	Sep. 30, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Deferred gain of the 2023 Series D Notes (due May 2023)	$ 21,023,000	$ 0
Convertible Notes Payable
Debt Instrument [Line Items]
Aggregate principal amount	200,928,000	213,959,000
Less unamortized discounts and debt issuance costs	(23,133,000)	(27,589,000)
Total net carrying value	198,818,000	186,370,000
Convertible Notes Payable \| Revolving Credit Facility
Debt Instrument [Line Items]
Aggregate principal amount	25,000,000	25,000,000
Convertible Notes Payable \| Senior Notes, due May 2023
Debt Instrument [Line Items]
Aggregate principal amount		66,090,000
Convertible Notes Payable \| Series B Senior Unsecured Convertible Notes
Debt Instrument [Line Items]
Aggregate principal amount		34,405,000
Convertible Notes Payable \| Series C Senior Convertible Notes due 2023
Debt Instrument [Line Items]
Aggregate principal amount	50,323,000
Convertible Notes Payable \| Series D Senior Convertible Notes
Debt Instrument [Line Items]
Aggregate principal amount	26,396,000
Convertible Notes Payable \| Senior Notes, due February 2023
Debt Instrument [Line Items]
Aggregate principal amount	$ 99,200,000	$ 88,464,000

Convertible Debt, Deferred Gain (Loss)

No definition available.

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- Definition

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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
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-Section S99
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-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

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- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
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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.

+ References

No definition available.

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
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