Stockholders' Equity - Stock Options Activities (Details) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021 USD ($) $ / shares shares	Dec. 31, 2020 USD ($) $ / shares shares
Number
Options outstanding, Balance (in shares) | shares	1,022,763
Granted (in shares) | shares	0
Exercised (in shares) | shares	(187,225)
Forfeited and expired (in shares) | shares	(3,000)
Options outstanding, Balance (in shares) | shares	832,538	1,022,763
Weighted average exercise price
Options outstanding, weighted average exercise price (in dollars per share) | $ / shares	$ 6.862
Granted, weighted average exercise price (in dollars per share) | $ / shares	0
Exercised, weighted average exercise price (in dollars per share) | $ / shares	6.417
Forfeited and expired, weighted average exercise price (in dollars per share) | $ / shares	2.077
Options outstanding, weighted average exercise price (in dollars per share) | $ / shares	$ 6.979	$ 6.862
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Options exercisable at the end of the year (in shares) | shares	814,082
Options exercisable at the end of the year, weighted average exercise price (in dollars per share) | $ / shares	$ 7.009
Options outstanding, aggregate intrinsic value | $	$ 44,849	$ 47,417
Options exercisable at the end of the year, aggregate intrinsic value | $	$ 43,831
Options outstanding, weighted average remaining contractual life (Year)	2 years 11 months 4 days	3 years 5 months 12 days
Options exercisable at the end of the year, weighted average remaining contractual life (Year)	2 years 9 months 21 days