Collaboration and Commercial Technology Licensing Agreements (Cleveland Diagnostics) (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Nov. 30, 2017	Dec. 31, 2017	Mar. 31, 2018
Collaboration agreements
Debt securities investment			$ 84,511
Exclusive licensing agreement with Cleveland Diagnostics
Collaboration agreements
Debt securities investment		$ 1,300	$ 1,400
Exclusive licensing agreement with Cleveland Diagnostics | Convertible promissory notes
Collaboration agreements
Amount invested in notes		$ 2,000
Cash obligation upon achievement of certain milestones	$ 18,500
Exclusive licensing agreement with Cleveland Diagnostics | Future plan | Convertible promissory notes
Collaboration agreements
Amount invested in notes	$ 3,000