Convertible Notes - Interest Expense Incurred (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]
Accrued coupon interest expense	$ 1,471	$ 1,471	$ 4,413	$ 4,413
Amortization of debt discounts	1,453	1,280	4,227	3,722
Amortization of deferred financing offering costs	191	166	552	485
Total convertible notes interest expense	3,115	2,917	9,192	8,620
Related Party
Debt Instrument [Line Items]
Accrued coupon interest expense	138	137	412	411
Amortization of debt discounts	135	120	393	350
Amortization of deferred financing offering costs	4	3	11	9
Total convertible notes interest expense	277	260	816	770
Others
Debt Instrument [Line Items]
Accrued coupon interest expense	1,333	1,334	4,001	4,002
Amortization of debt discounts	1,318	1,160	3,834	3,372
Amortization of deferred financing offering costs	187	163	541	476
Total convertible notes interest expense	$ 2,838	$ 2,657	$ 8,376	$ 7,850