Stock-based Compensation - Stock Option Activity (Details) $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2020 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares
Number of Shares
Beginning balance - Outstanding (shares) | shares	526,070
Granted (shares) | shares	278,537
Exercised (shares) | shares	(166)
Forfeited/Cancelled(shares) | shares	(22,756)
Ending balance - Outstanding (shares) | shares	781,685	526,070
Exercisable (shares) | shares	385,059
Vested or expected to vest (shares) | shares	781,685
Weighted- Average Exercise Price
Beginning balance - Outstanding (in dollars per share) | $ / shares	$ 30.55
Granted (in dollars per share) | $ / shares	8.59
Exercised (in dollars per share) | $ / shares	8.60
Forfeited/Cancelled (in dollars per share) | $ / shares	20.66
Ending balance - Outstanding (in dollars per share) | $ / shares	23.01	$ 30.55
Exercisable (in dollars per share) | $ / shares	35.22
Vested or expected to vest (in dollars per share) | $ / shares	$ 23.01
Weighted- Average Remaining Contractual Life (in years)
Balance - Outstanding	7 years 7 months 6 days	7 years 7 months 13 days
Exercisable	6 years 5 months 1 day
Vested or expected to vest	7 years 7 months 6 days
Aggregate Intrinsic Value ($000)
Balance - Outstanding | $	$ 21	$ 60
Exercisable | $	19
Vested and expected to vest | $	$ 21