Convertible Notes Schedule of interest expense for December 2021 Notes (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Adjustments to Additional Paid in Capital, Convertible Debt with Conversion Feature	$ 5,967	$ 620	$ 100
February 2018 Notes [Member]
Debt Instrument [Line Items]
Contractual coupon interest	4,125	447
Amortization of debt issuance costs	74	10
Amortization of Debt Discount (Premium)	526	75
Interest Expense, Debt	$ 10,692	$ 1,152

Amortization of debt issuance costs

No definition available.

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- Definition

Amount of increase (decrease) in additional paid in capital (APIC) resulting from recognition of deferred taxes for convertible debt with a beneficial conversion feature.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
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-URI http://asc.fasb.org/extlink&oid=75116239&loc=d3e34017-109320

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Beneficial Conversion Feature
-URI http://asc.fasb.org/extlink&oid=6505963

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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Subparagraph (b)
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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.

+ Details

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- Definition

Amount of the cost of borrowed funds accounted for as interest expense for debt.

+ References

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-Topic 225
-SubTopic 10
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-Paragraph 2
-Subparagraph (SX 210.5-03.8)
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- Definition

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.

+ References

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-Paragraph 2
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