Revenue Recognition - Impact to Financial Statements (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Revenues:
Product revenue	$ 6,163	$ 5,586
Research and development revenue	7,879	2,385
Total revenues	14,042	7,971
Costs and operating expenses:
Cost of product revenue	3,825	3,002
Research and development	7,178	5,839
Selling, general and administrative	7,746	6,606
Total costs and operating expenses	18,749	15,447
Loss from operations	(4,707)	(7,476)
Interest income	71	18
Other expenses	(60)	22
Loss before income taxes	(4,696)	(7,436)
Provision (benefit) from income taxes	(2)	24
Net loss	$ (4,694)	$ (7,460)
Net loss per share, basic and diluted (usd per shares)	$ (0.10)	$ (0.18)
Weighted average common stock shares used in computing net income (loss) per share, basic (shares)	48,385
Assets
Accounts Receivable	$ 8,974		$ 11,800
Other non-current assets	470		302
Liabilities
Other accrued liabilities	5,304		4,362
Deferred revenue	7,518		12,292
Deferred revenue, net of current portion	5,529		1,501
Stockholders' equity:
Accumulated deficit	(324,291)		(315,065)
Balances without adoption of Topic 606 [Member]
Revenues:
Product revenue	3,648
Research and development revenue	6,557
Total revenues	10,205
Costs and operating expenses:
Cost of product revenue	2,540
Research and development	7,131
Selling, general and administrative	7,746
Total costs and operating expenses	17,417
Loss from operations	(7,212)
Interest income	71
Other expenses	(60)
Loss before income taxes	(7,201)
Provision (benefit) from income taxes	(2)
Net loss	$ (7,199)
Net loss per share, basic and diluted (usd per shares)	$ (0.15)
Weighted average common stock shares used in computing net income (loss) per share, basic (shares)	48,385
Assets
Accounts Receivable	$ 7,910
Other non-current assets	278
Liabilities
Other accrued liabilities	3,782
Deferred revenue	9,451
Deferred revenue, net of current portion	2,308
Stockholders' equity:
Accumulated deficit	(322,737)
Accounting Standards Update 2014-09 [Member] | Adjustments [Member]
Revenues:
Product revenue	2,515
Research and development revenue	1,322
Total revenues	3,837
Costs and operating expenses:
Cost of product revenue	1,285
Research and development	47
Selling, general and administrative	0
Total costs and operating expenses	1,332
Loss from operations	2,505
Interest income	0
Other expenses	0
Loss before income taxes	2,505
Provision (benefit) from income taxes	0
Net loss	$ 2,505
Net loss per share, basic and diluted (usd per shares)	$ 0.05
Assets
Accounts Receivable	$ 1,064
Other non-current assets	192
Liabilities
Other accrued liabilities	1,522
Deferred revenue	(1,933)
Deferred revenue, net of current portion	3,221
Stockholders' equity:
Accumulated deficit	$ (1,554)		$ (4,100)