Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Revenue:
Total revenue	$ 42,658	$ 29,426	$ 103,990	$ 88,041
Costs and expenses:
Selling and marketing	16,556	14,654	50,107	42,928
General and administrative	17,001	13,012	49,926	34,739
Research and development	22,399	17,238	68,657	49,194
Total costs and expenses	75,084	60,850	227,417	166,152
Loss from operations	(32,426)	(31,424)	(123,427)	(78,111)
Interest (expense) income, net	(278)	142	(132)	528
Other income	60		204
Net loss	(32,644)	(31,282)	(123,355)	(77,583)
Other comprehensive income (loss):
Unrealized gain/(loss) on available-for-sale securities	15	(25)	9	212
Foreign currency translation adjustment	(2)		83
Total other comprehensive income (loss)	13	(25)	92	212
Comprehensive loss	$ (32,631)	$ (31,307)	$ (123,263)	$ (77,371)
Net loss per common share, basic and diluted	$ (0.90)	$ (0.90)	$ (3.45)	$ (2.24)
Weighted-average common shares outstanding, basic and diluted	36,086,169	34,949,785	35,726,711	34,701,013
Molecular Information Services [Member]
Revenue:
Revenue	$ 22,750	$ 13,754	$ 63,121	$ 45,130
Costs and expenses:
Cost of molecular information services	17,890	14,729	54,544	36,241
Pharma Research and Development Services [Member]
Revenue:
Revenue	3,269	2,571	5,571	9,330
Roche [Member] | Molecular Information Services [Member]
Revenue:
Related-party revenue	5,618	4,965	16,642	16,201
Costs and expenses:
Cost of related-party molecular information services from Roche	1,238	1,217	4,183	3,050
Roche [Member] | Pharma Research and Development Services [Member]
Revenue:
Related-party revenue	$ 11,021	$ 8,136	$ 18,656	$ 17,380