Intangible Assets and Goodwill - Summary of Carrying Value of Intangible Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Indefinite-lived Intangible Assets [Line Items]
Intangible assets	$ 43,836	$ 58,647
IPR&D – Immune Modulators
Indefinite-lived Intangible Assets [Line Items]
Intangible assets	0	0
IPR&D – Antigen Inhibitors
Indefinite-lived Intangible Assets [Line Items]
Intangible assets	0	14,811
IPR&D – cccDNA Sterilizers
Indefinite-lived Intangible Assets [Line Items]
Intangible assets	$ 43,836	$ 43,836