Stock-Based Compensation - Stock option activity (Details) - $ / shares	1 Months Ended	3 Months Ended		9 Months Ended
	May 31, 2014	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Shares Available for Grant
Beginning of the period (in shares)				196,982
Additional shares reserved (in shares)	77,908			562,736
Options granted (in shares)		(26,677)	(201,082)	(200,177)	(584,957)
Options exercised (in shares)		0	3,117	4,913	5,650
Options cancelled (in shares)				31,598
End of the period (in shares)		591,139		591,139
Number of options
Number of Shares, beginning of the period (in shares)				1,380,312
Number of Shares, Stock option granted		26,677	201,082	200,177	584,957
Number of Shares, Options exercised (in shares)				(4,913)
Number of Shares, Options cancelled (in shares)				(31,598)
Number of Shares, end of the period (in shares)		1,543,978		1,543,978
Weighted average exercise price
Weighted-Average Exercise Price, beginning of the period (in dollars per share)				$ 10.06
Weighted-Average Exercise Price, Options granted (in dollars per share)				5.85
Weighted-Average Exercise Price, Options exercised (in dollars per share)				2.89
Weighted-Average Exercise Price, Options cancelled (in dollars per share)				14.65
Weighted-Average Exercise Price, end of the period (in dollars per share)		$ 9.44		$ 9.44