Convertible Debt - Schedule of Interest Expense Related to Notes (Details) - Convertible Debt - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
2017 Notes
Debt Instrument [Line Items]
Contractual interest expense	$ 1,617	$ 1,617	$ 1,491
Interest cost related to amortization of the debt discount	20,080	18,910	4,338
Total interest expense	21,697	20,527	$ 5,829
2018 Notes
Debt Instrument [Line Items]
Contractual interest expense	6,469	1,455
Interest cost related to amortization of the debt discount	26,161	2,207
Total interest expense	32,630	$ 3,662
2019 Notes
Debt Instrument [Line Items]
Contractual interest expense	3,342
Interest cost related to amortization of the debt discount	12,205
Total interest expense	$ 15,547