Stock-Based Compensation - Restricted stock unit activity (Details) - Restricted Stock Units $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2020 USD ($) $ / shares shares
Shares
Outstanding, beginning balance (in shares) | shares	808,424
Granted (in shares) | shares	426,107
Vested (in shares) | shares	(249,936)
Cancelled (in shares) | shares	(28,691)
Outstanding, ending balance (in shares) | shares	955,904
Weighted- Average Grant- Date Fair Value
Outstanding, beginning balance (in dollars per share) | $ / shares	$ 27.94
Granted (in dollars per share) | $ / shares	18.99
Vested (in dollars per share) | $ / shares	26.50
Cancelled (in dollars per share) | $ / shares	26.08
Outstanding, ending balance (in dollars per share) | $ / shares	$ 24.11
Weighted-Average Remaining Contractual Term (Years), Outstanding	3 years 4 months 24 days
Aggregate Intrinsic Value, Vested | $	$ 5,379
Aggregate Intrinsic Value, Outstanding | $	$ 16,183