Convertible Senior Notes - Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016
Long-term debt
Amortization of debt issuance costs	$ 80	$ 72
Convertible debt \| 3.00% Convertible senior notes due 2022
Long-term debt
Contractual interest expense	1,110	1,116
Amortization of debt issuance costs	80	72
Amortization of debt discount	1,600	1,446
Total	$ 2,790	$ 2,634
Effective interest rate of the liability component	11.00%	11.00%

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.

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Amount of amortization expense attributable to debt issuance costs.

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

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

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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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