Stock-Based Compensation - Restricted stock units activity (Details) - Restricted Stock Units $ / shares in Units, $ in Millions	6 Months Ended
	Jun. 30, 2020 USD ($) $ / shares shares
Number of shares
Non vested outstanding at beginning of period | shares	6,066
Restricted stock units granted (in shares) | shares	1,795
Restricted stock units vested (in shares) | shares	(6,066)
Non vested at end of period | shares	1,795
Weighted-average grant date fair value
Non vested outstanding at beginning of period (per share) | $ / shares	$ 16.49
Restricted stock units granted (per share) | $ / shares	73.60
Restricted stock units vested (per share) | $ / shares	16.49
Non vested outstanding at end of period (per share) | $ / shares	$ 73.60
Total unrecognized stock-based compensation expense | $	$ 0.1
Weighted-average period over which unrecognized stock-based compensation expense is expected to be recognized	10 months 21 days