Intangible Assets - Carrying Value and Accumulated Amortization (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	$ 252,458	$ 252,458
Accumulated Amortization	(33,460)	(27,186)
Net Carrying Value	218,998	225,272
Developed Technology Rights | JUXTAPID
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	42,300	42,300
Accumulated Amortization	(5,246)	(4,262)
Net Carrying Value	37,054	38,038
Developed Technology Rights | MYALEPT
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	210,158	210,158
Accumulated Amortization	(28,214)	(22,924)
Net Carrying Value	$ 181,944	$ 187,234