Notes Payable - Convertible Senior Notes - Total Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Interest Expense
Contractual interest expense	$ 1,804	$ 1,805
Amortization of debt issuance costs	398	346
Amortization of debt discount	5,424	5,069
Total interest expense	$ 7,626	$ 7,220