Debt - Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Term Loan | Secured Debt
Debt Instrument [Line Items]
Contractual interest expense	$ 516	$ 1,210	$ 1,667	$ 2,390
Amortization of debt discount	526	333	859	666
Amortization of debt issuance costs	63	40	103	80
Total interest expense	1,105	1,583	2,629	3,136
2025 Notes | Convertible Debt
Debt Instrument [Line Items]
Contractual interest expense	800		800
Amortization of debt discount	124		124
Amortization of debt issuance costs	96		96
Total interest expense	1,020		1,020
2022 Notes | Convertible Debt
Debt Instrument [Line Items]
Contractual interest expense	286	1,445	768	2,891
Amortization of debt discount	700	1,955	1,952	3,911
Amortization of debt issuance costs	39	115	111	229
Total interest expense	$ 1,025	$ 3,515	$ 2,831	$ 7,031