Revenue from Contracts with Customers - Schedule of Impact of Changes in Accounting Standard (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Product and service	$ 20,384	$ 18,310	$ 38,429	$ 34,075
Collaboration	4,615	16,282	9,655	18,581
Total revenue	24,999	34,592	48,084	52,656
Net loss	$ (20,601)	$ (4,555)	$ (39,803)	$ (23,407)
Net loss per share - basic and diluted (in dollars per share)	$ (0.80)	$ (0.20)	$ (1.55)	$ (1.06)
Deferred revenue, current portion	$ 9,878		$ 9,878		$ 9,229
Accumulated deficit	(353,659)		(353,659)		$ (313,102)
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Product and service	160		399
Collaboration	0		0
Total revenue	160		399
Net loss	$ 160		$ 399
Net loss per share - basic and diluted (in dollars per share)	$ 0.01		$ 0.02
Deferred revenue, current portion	$ 355		$ 355
Accumulated deficit	(355)		(355)
Calculated under Revenue Guidance in Effect before Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Product and service	20,224		38,030
Collaboration	4,615		9,655
Total revenue	24,839		47,685
Net loss	$ (20,761)		$ (40,202)
Net loss per share - basic and diluted (in dollars per share)	$ (0.81)		$ (1.57)
Deferred revenue, current portion	$ 9,523		$ 9,523
Accumulated deficit	$ (353,304)		$ (353,304)