Amount of noncash expense included in interest expense to amortize debt discount and premium associated with the related debt instruments. Excludes amortization of financing costs. Alternate captions include noncash interest expense.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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-Section S99
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Carrying value as of the balance sheet date of the portion of long-term debt due within one year or the operating cycle if longer identified as Convertible Notes Payable. Convertible Notes Payable is a written promise to pay a note which can be exchanged for a specified amount of another, related security, at the option of the issuer and the holder.

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Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
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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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No definition available.

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Represents the portion of interest incurred in the period on debt arrangements that was charged against earnings, excluding amortization of debt discount (premium) and financing costs.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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Convertible Debt (Details) - USD ($) $ in Thousands	12 Months Ended
Convertible Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2014
2015 Convertible Senior Notes
Debt Instrument [Line Items]
Convertible senior notes, current		$ 18,000
Convertible Senior Notes [Member] \| 2015 Convertible Senior Notes
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Effective Percentage		4.50%	4.50%
Convertible Senior Notes [Member] \| 2013 Convertible Senior Notes [Member]
Debt Instrument [Line Items]
Contractually stated interest costs	$ 101
Amortization of interest costs	$ 7