Debt - Schedule of Interest Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Total amortization of debt issuance costs and accretion of equity portion	$ 6,385	$ 2,584	$ 0
Total interest expense related to the convertible senior notes	8,928	3,681	$ 0
1.75% Convertible Senior Notes due 2023
Debt Instrument [Line Items]
Amortization of debt discount	5,405	2,280
Amortization of debt issuance costs	724	304
Total amortization of debt issuance costs and accretion of equity portion	6,129	2,584
Contractual interest expense	2,516	1,097
Total interest expense related to the convertible senior notes	$ 8,645	$ 3,681