Debt - Total Interest Expense Recognized Related to the Convertible Debt (Details) - Convertible Debt - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Debt Instrument [Line Items]
Contractual interest expense	$ 2,600	$ 2,600	$ 7,800	$ 7,867
Amortization of debt issuance costs	388	353	1,137	1,051
Amortization of debt discount	3,810	3,466	11,164	10,281
Total interest expense	$ 6,798	$ 6,419	$ 20,101	$ 19,199