License Agreements (Summarized Financial Information for MeiraGTx) (Details) - MeiraGTx Ltd. [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Cash	$ 8,549	$ 17,477
Other current assets	2,926	1,613
Noncurrent assets	14,379	3,461
Current liabilities	21,402	6,041
Noncurrent liabilities	479	815
Mezzanine equity	51,410	33,002
Total stockholders’ equity	(47,437)	(17,308)
General and administrative expense	9,879	6,027
Research and development expense	22,414	14,038
Net loss attributable to non‑controlling interest in subsidiary and other	$ (32,717)	$ (19,792)