Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenue:
Total revenue	$ 52,840	$ 26,328
Costs and expenses:
Selling and marketing	17,480	16,436
General and administrative	20,695	15,277
Research and development	23,859	23,285
Total costs and expenses	89,261	73,015
Loss from operations	(36,421)	(46,687)
Interest (expense) income, net	(994)	90
Other income		144
Net loss	(37,415)	(46,453)
Other comprehensive loss:
Unrealized loss on available-for-sale securities		(18)
Foreign currency translation adjustment	(286)	(17)
Total other comprehensive loss	(286)	(35)
Comprehensive loss	$ (37,701)	$ (46,488)
Net loss per common share, basic and diluted	$ (1.02)	$ (1.31)
Weighted-average common shares outstanding, basic and diluted	36,792,980	35,426,296
Molecular Information Services [Member]
Revenue:
Revenue	$ 31,943	$ 15,594
Costs and expenses:
Cost of molecular information services	21,279	17,117
Pharma Research and Development Services [Member]
Revenue:
Revenue	4,782	1,087
Roche [Member] | Molecular Information Services [Member]
Revenue:
Related-party revenue	14,648	5,504
Costs and expenses:
Cost of related-party molecular information services from Roche	5,948	900
Roche [Member] | Pharma Research and Development Services [Member]
Revenue:
Related-party revenue	$ 1,467	$ 4,143