Supplementary Data — Quarterly Financial Data (unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
General and administrative	$ 6,042	$ 5,711	$ 5,500	$ 5,579	$ 5,446	$ 5,266	$ 4,927	$ 5,837	$ 22,832	$ 21,476	$ 17,354
Sales and marketing	2,724	2,367	2,181	2,162	1,903	1,873	1,858	1,912	9,434	7,546	9,391
Research and development	7,048	6,620	5,480	4,254	5,220	4,270	3,605	3,917	23,402	17,012	13,443
Amortization of intangible assets	106	156	157	156	156	158	158	158	575	630	631
Operating Expenses	15,920	14,854	13,318	12,151	12,725	11,567	10,548	11,824	56,243	46,664	40,819
Total operating expenses	(911)	4,571	3,995	2,709	1,420	5,650	4,240	(1,331)	10,364	9,978	9,249
Provision for (benefit from) income taxes	116	(83)	756	554	(516)	1,339	(11,122)	(357)	1,343	(10,653)	(8,425)
Income (loss) from operations	$ (609)	$ 5,149	$ 3,719	$ 2,654	$ 2,421	$ 4,658	$ 15,743	$ (726)	$ 10,913	$ 22,093	$ 18,354
Basic (in dollars per share)	$ (0.01)	$ 0.09	$ 0.07	$ 0.05	$ 0.04	$ 0.09	$ 0.29	$ (0.01)	$ 0.20	$ 0.41	$ 0.34
Diluted (in dollars per share)	$ (0.01)	$ 0.09	$ 0.07	$ 0.05	$ 0.04	$ 0.08	$ 0.28	$ (0.01)	$ 0.19	$ 0.40	$ 0.33
Tax Cuts and Jobs Act, incomplete accounting, change in tax rate, provisional income tax expense (benefit)							$ (12,100)				$ 2,500
Tax Cuts And Jobs Act Of 2017, incomplete accounting, change in tax rate, deferred tax asset, provisional income tax expense (benefit)							(11,900)
License and development revenue
Revenue	$ 3,717	$ 3,098	$ 3,570	$ 3,723	$ 3,723	$ 3,661	3,358	$ 2,749			11,106
Product
Revenue	15,784	21,752	19,226	16,072	13,983	18,578	17,406	11,058			58,023
Product cost of revenue	4,492	5,425	5,483	4,935	3,561	5,022	5,976	3,314	$ 20,335	$ 17,873	19,061
Product gross profit	$ 11,292	$ 16,327	$ 13,743	$ 11,137	$ 10,422	$ 13,556	$ 11,430	$ 7,744	$ 52,499	$ 43,152	$ 38,962