Debt (Details) - Convertible Debt - USD ($) $ in Thousands		Dec. 31, 2020	Dec. 31, 2019
Debt (Details) - Convertible Debt [Line Items]
Principal/ Fair Value Amount		$ 34,134	$ 52,658
Debt Issuance Costs		0	0
Net Amount		34,134	52,658
4.875% Convertible Senior Notes Due 2020 [Member]
Debt (Details) - Convertible Debt [Line Items]
Principal/ Fair Value Amount		0	1,905
Debt Issuance Costs		0	0
Net Amount		0	1,905
3.25% Convertible Senior Notes Due 2023 [Member]
Debt (Details) - Convertible Debt [Line Items]
Principal/ Fair Value Amount	[1]	34,134	50,753
Debt Issuance Costs	[1]	0	0
Net Amount	[1]	$ 34,134	$ 50,753

[1] The amounts presented for the 3.25% convertible senior notes due 2023 within the table represent the fair value as of December 31, 2020 and 2019 (see Note 16 - Fair Value Measurements). The principal amount of these notes is $22.9 million and $37.6 million as of December 31, 2020 and 2019, respectively. The accrued, but unpaid, payment-in-kind interest is $0.9 million and $0.4 million as of December 31, 2020 and 2019, respectively.