Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		12 Months Ended
		Dec. 31, 2020		Dec. 31, 2019	Dec. 31, 2018	Sep. 25, 2020
Earnings Per Share [Abstract]
Stock dividend, percent		300.00%	[1]	300.00%	300.00%	300.00%
Net Income		$ 40,827		$ 37,475	$ 36,279
Weighted Average Shares - Basic (in shares)	[2]	15,465		15,388	15,285
Earnings Per Share - Basic (in dollars per share)	[2]	$ 2.64		$ 2.44	$ 2.37
Dilutive Average Shares Attributable to Stock Options (in shares)		14		45	85
Weighted Average Shares - Diluted (in shares)	[2]	15,479		15,433	15,370
Earnings Per Share - Diluted (in dollars per share)	[2]	$ 2.64		$ 2.43	$ 2.36

[1] Included in the shares issued for the 3% stock dividend in 2020 were treasury shares of 137,041

[2] Share and Per Share Amounts have been restated for the September 25, 2020 3% stock dividend.