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Long-Term Debt Senior Convertible Notes (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2018 | Sep. 30, 2017 | Sep. 30, 2018 | Sep. 30, 2017 | Dec. 31, 2017
Debt Instrument [Line Items] |  |  |  |  |
Senior Convertible Notes, net carrying amount | $ 145,662 |  | $ 145,662 |  | $ 139,107
1.50% Senior Convertible Notes Due 2021 [Member] |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Senior Convertible Notes, face amount | $ 172,500 |  | $ 172,500 |  | 172,500
Senior Convertible Notes, interest rate, stated percentage | 1.50% |  | 1.50% |  |
Senior Convertible Notes, interest expense | $ 2,600 | $ 2,500 | $ 7,800 | $ 7,400 |
Senior Convertible Notes, unamortized debt discount | (24,316) |  | (24,316) |  | (30,183)
Unamortized deferred financing costs | (2,522) |  | (2,522) |  | (3,210)
Senior Convertible Notes, net carrying amount | $ 145,662 |  | $ 145,662 |  | $ 139,107

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- Definition Carrying amount of long-term convertible debt as of the balance sheet date, net of the amount due in the next twelve months or greater than the normal operating cycle, if longer. The debt is convertible into another form of financial instrument, typically the entity's common stock. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition Contractual interest rate for funds borrowed, under the debt agreement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(1)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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