Collaboration and Commercial Technology Licensing Agreements (Biocartis) (Details) $ / shares in Units, $ in Thousands, € in Millions	1 Months Ended		3 Months Ended		12 Months Ended
	Dec. 31, 2017 EUR (€)	Dec. 31, 2017 USD ($) $ / shares shares	Mar. 31, 2018 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2017 EUR (€)	Dec. 31, 2017 USD ($) $ / shares shares	Sep. 30, 2017 EUR (€)
Collaboration agreements
Amount invested			$ 24,043	$ 20,599
Exclusive license and development agreement with Biocartis NV
Collaboration agreements
Number of shares purchased | shares		270,000				270,000
Market price | $ / shares		$ 12.50				$ 12.50
Amount invested	€ 3.4	$ 4,000
Estimated fair value		$ 3,500	$ 3,800			$ 3,500
Cash obligation upon achievement of certain milestones | €							€ 6.5
Exclusive license and development agreement with Biocartis NV | Research and development
Collaboration agreements
Upfront license and option fee payment					€ 2.8	$ 3,200