Intangible Assets (Details) - USD ($) $ in Thousands		3 Months Ended
	Mar. 31, 2018	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Intangible Assets
Acquired and in-licensed rights	$ 64,665	$ 64,665		$ 64,665
Less: accumulated amortization	(9,718)	(9,718)		(8,281)
Total intangible asset, net	54,947	54,947		$ 56,384
Amortization expense	1,400		$ 500
Estimated future amortization expense
2018	4,500	4,500
2019	6,000	6,000
2020	6,000	6,000
2021	6,000	6,000
2022	6,000	6,000
Thereafter	$ 26,500	$ 26,500
Use Rights [Member] | Minimum
Intangible Assets
Estimated useful life		8 years
Use Rights [Member] | Maximum
Intangible Assets
Estimated useful life		15 years