Stockholders' equity - Additional Information (Details) $ / shares in Units, $ in Thousands						12 Months Ended
	Jul. 07, 2020 USD ($) $ / shares shares	Dec. 20, 2019 USD ($) $ / shares shares	Dec. 17, 2019 $ / shares shares	Nov. 12, 2019 shares	Aug. 08, 2019 shares	Dec. 31, 2020 USD ($) offering $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, shares authorized (in shares)						100,000,000	100,000,000
Common stock, par value (in dollars per share) | $ / shares						$ 0.000001	$ 0.000001
Common stock, shares issued (in shares)						42,196,296	37,996,849
Common stock, shares outstanding (in shares)						42,196,296	37,996,849
Proceeds from issuance of common stock | $	$ 71,300	$ 80,700				$ 71,675	$ 81,043
Public offering costs | $	$ 4,900	$ 5,500				$ 355	$ 352
Preferred stock, shares authorized (in shares)						5,000,000	5,000,000
Preferred stock, par value (in dollars per share) | $ / shares						$ 0.000001	$ 0.000001
Preferred stock, shares issued (in shares)						0	0
Preferred stock, shares outstanding (in shares)						0	0
Stock conversion ratio					100
Conversion of common stock to pre-funded warrants (in shares)			10,925,481
Maximum percentage of outstanding stock per stockholder			9.99%
Options outstanding (in shares)						6,846,289	5,840,538
Options exercised (in shares)						882,624
Common stock issued upon exercise of options aggregate intrinsic value | $						$ 6,000	$ 1,300
Weighted-average grant date fair value of options granted (in dollars per share) | $ / shares						$ 8.70	$ 2.17
Unrecognized stock-based compensation cost (in dollars per share) | $						$ 24,900
Unrecognized stock-based compensation cost, weighted-average period recognized (in years)						3 years 1 month 24 days
Issuance of common stock under Employee Stock Purchase Plan (in shares)						18,352
Issuance of common stock under Employee Stock Purchase Plan | $						$ 199
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period						1 year
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period						4 years
2014 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum number of shares of common stock that may be issued (in shares)						9,786,363
Years of increase in shares of common stock reserved for issuance						10 years
Shares of common stock reserved for issuance percentage						4.00%
Number of additional shares authorized (in shares)				4,500,000
Award expiration period (in years)						10 years
Shares available to be granted (in shares)						6,037,532	6,556,534
Equity Incentive Plan 2006
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options outstanding (in shares)						23,958
Non-voting convertible preferred stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Preferred stock, shares outstanding (in shares)						0
Stock issued for acquisition (in shares)							102,000
Shares to be converted				101,927
Pre funded common stock warrants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of common stock in prefunded warrants (in shares)			10,925,481
Exercise price (in dollars per share) | $ / shares			$ 0.000001
Common stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Sale of shares under public offering (in shares)						3,262,471	10,263,750
Stock issued for acquisition (in shares)							4,589,771
Convertible preferred stock, Shares issued upon conversion (in shares)				10,192,700
Conversion of common stock to pre-funded warrants (in shares)							(10,925,481)
Options exercised (in shares)						882,624	326,094
Issuance of common stock under Employee Stock Purchase Plan (in shares)						18,352
Aquinox | Non-voting convertible preferred stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock issued for acquisition (in shares)					101,927
Aquinox | Common stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock issued for acquisition (in shares)					4,589,771
Pre-funded warrants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of common stock in prefunded warrants (in shares)	1,737,529
Pre funded warrant issued (in dollars per share) | $ / shares	$ 15.249999
Exercise price (in dollars per share) | $ / shares	$ 0.000001
Shares issuable under 2020 ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Sale of shares under public offering (in dollars per share) | $ / shares						$ 10.84
Shares issuable under 2020 ESPP | 2020 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
ESPP common stock reserved for issuance (in shares)						759,936
ESPP max contribution rate						15.00%
ESPP purchase price of common stock, percent of market price						85.00%
ESPP number of offerings per year | offering						2
ESPP offering period						6 months
Public Stock Offering
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Sale of shares under public offering (in shares)	3,262,471	10,263,750
Sale of shares under public offering (in dollars per share) | $ / shares	$ 15.25	$ 8.40