Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Income Statement [Abstract]
Revenue	$ 16,681	$ 17,423
Related-party revenue from Roche	9,647	12,955
Total revenue	26,328	30,378
Costs and expenses:
Cost of revenue	17,117	10,028
Cost of Roche related-party revenue	900	1,362
Selling and marketing	16,436	13,793
General and administrative	15,277	9,224
Research and development	23,285	13,456
Total costs and expenses	73,015	47,863
Loss from operations	(46,687)	(17,485)
Interest income, net	90	178
Other income	144
Net loss	(46,453)	(17,307)
Other comprehensive (loss)/gain income:
Unrealized (loss)/gain on available-for-sale securities	(18)	164
Foreign currency translation adjustment	(17)
Total other comprehensive (loss) income	(35)	164
Comprehensive loss	$ (46,488)	$ (17,143)
Net loss per common share, basic and diluted	$ (1.31)	$ (0.50)
Weighted-average common shares outstanding, basic and diluted	35,426,296	34,537,007