Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Total revenue	$ 35,004	$ 28,237	$ 61,332	$ 58,615
Costs and expenses:
Selling and marketing	17,115	14,481	33,551	28,274
General and administrative	17,648	12,503	32,925	21,727
Research and development	22,973	18,500	46,258	31,956
Total costs and expenses	79,318	57,439	152,333	105,302
Loss from operations	(44,314)	(29,202)	(91,001)	(46,687)
Interest income, net	56	208	146	386
Other income			144
Net loss	(44,258)	(28,994)	(90,711)	(46,301)
Other comprehensive income:
Unrealized gain/(loss) on available-for-sale securities	12	73	(6)	237
Foreign currency translation adjustment	102		85
Total other comprehensive income	114	73	79	237
Comprehensive loss	$ (44,144)	$ (28,921)	$ (90,632)	$ (46,064)
Net loss per common share, basic and diluted	$ (1.24)	$ (0.84)	$ (2.55)	$ (1.34)
Weighted-average common shares outstanding, basic and diluted	35,660,430	34,613,513	35,544,003	34,575,260
Molecular Information Services [Member]
Revenue	$ 24,777	$ 17,001	$ 40,371	$ 31,376
Costs and expenses:
Cost of molecular information services	19,537	11,484	36,654	21,512
Pharma Research and Development Services [Member]
Revenue	1,215	3,711	2,302	6,759
Roche [Member] | Molecular Information Services [Member]
Related-party revenue	5,520	5,682	11,024	11,236
Costs and expenses:
Cost of related-party molecular information services from Roche	2,045	471	2,945	1,833
Roche [Member] | Pharma Research and Development Services [Member]
Related-party revenue	$ 3,492	$ 1,843	$ 7,635	$ 9,244