Current and Long-Term Debt - Convertible Notes Interest Expense (Details) - Convertible Senior Notes 1.00 percent due December 2020 - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Long-Term Debt
Cash interest per contractual coupon rate	$ 686	$ 719	$ 1,405	$ 1,438
Amortization of note discount	2,968	2,816	5,898	5,596
Amortization of debt issuance costs	233	211	461	417
Total interest expense related to Convertible Notes	$ 3,887	$ 3,746	$ 7,764	$ 7,451

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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