Stock-based compensation - Summary of Service-based Stock Option Activity and Related Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2019	Mar. 31, 2020
Options outstanding
Exercised (in shares)	(62,450)
Weighted-average exercise price
Exercised (in USD per share)	$ 1.84
Closing stock price (in USD per share)		$ 9.84
Service-based Stock Options
Options outstanding
Beginning balance (in shares)	2,746,670	2,575,579
Granted (in shares)	115,100	202,560
Exercised (in shares)		(334,572)
Canceled or forfeited (in shares)	(286,191)	(444,014)
Ending balance (in shares)	2,575,579	1,999,553
Options outstanding, Exercisable (in shares)		1,291,647
Weighted-average exercise price
Beginning balance (in USD per share)	$ 12.91	$ 12.24
Granted (in USD per share)	7.95	14.18
Exercised (in USD per share)		4.08
Canceled or forfeited (in USD per share)	16.98	15.07
Ending balance (in USD per share)	$ 12.24	13.17
Weighted-average exercise price, Exercisable (in USD per share)		$ 12.06
Weighted-average remaining contractual life (in years), Outstanding	6 years 10 months 24 days	6 years 9 months 7 days
Weighted-average remaining contractual life (in years), Exercisable		6 years 1 month 6 days
Aggregate intrinsic values, Outstanding	$ 6,958	$ 3,773
Aggregate intrinsic values, Exercisable		$ 3,469

The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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Balance Type:	na
Period Type:	instant

- Definition

The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.