Collaboration and Commercial Technology Licensing Agreements (Epic) (Details)	1 Months Ended		6 Months Ended		24 Months Ended
	Jun. 30, 2018 USD ($)	Jun. 30, 2016 USD ($) item	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)
Collaboration agreements
Debt securities investment	$ 95,447,000		$ 95,447,000
Amount invested			$ 64,388,000	$ 50,338,000
Exclusive distribution rights Epic's AR-V7 Nucleus Detect
Collaboration agreements
Amount invested in notes					$ 7,500,000
Debt securities investment					7,100,000
Deferred cost					$ 375,000
Investment in preferred stock per collaboration agreement		$ 2,500,000
Number of milestones needed to be achieved for conversion into preferred stock | item		1
Obligation upon achievement of certain milestones		$ 4,000,000
Term of agreement		10 years
Exclusive distribution rights Epic's AR-V7 Nucleus Detect | Corporate equity securities
Collaboration agreements
Amount invested	$ 2,500,000