Stockholders' Equity - Stock Options Activities (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares
Number
Options outstanding at the beginning of the year (in shares) | shares	454,348
Granted (in shares) | shares	10,933
Exercised (in shares) | shares	(123,751)
Forfeited (in shares) | shares	(609)
Options outstanding at the end of the period (in shares) | shares	340,921	454,348
Options exercisable at the end of the year (in shares) | shares	331,759
Weighted average exercise price
Options outstanding at the beginning of the year, weighted average exercise price (in dollars per share) | $ / shares	$ 20.628
Granted, weighted average exercise price (in dollars per share) | $ / shares	17.045
Exercised, weighted average exercise price (in dollars per share) | $ / shares	20.503
Forfeited, weighted average exercise price (in dollars per share) | $ / shares	11.618
Options outstanding at the end of the period, weighted average exercise price (in dollars per share) | $ / shares	20.586	$ 20.628
Options exercisable at the end of the year, weighted average exercise price (in dollars per share) | $ / shares	$ 20.684
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Options outstanding at the beginning of the year, aggregate intrinsic value | $	$ 48,760	$ 25,935
Options exercisable at the end of the year, aggregate intrinsic value | $	$ 47,417
Options outstanding at the beginning of the year, weighted average remaining contractual life (Year)	3 years 7 months 6 days	4 years 4 months 2 days
Options exercisable at the end of the year, weighted average remaining contractual life (Year)	3 years 5 months 12 days