Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share [Abstract]
Net Income (Loss) Attributable to Parent	$ 22,222	$ 20,126	$ 18,251	$ 28,996	$ 22,611	$ 22,371	$ 22,751	$ 21,619	$ 89,595	$ 89,352	$ 70,002
Undistributed Earnings (Loss) Allocated to Participating Securities, Basic									887	806	654
Distributed earnings allocated to common shares outstanding									35,745	35,542	32,483
Undistributed earnings allocated to common shares outstanding									52,963	53,004	36,865
Net earnings allocated to common shareholders	$ 21,992	$ 19,929	$ 18,051	$ 28,736	$ 22,372	$ 22,188	$ 22,553	$ 21,433	$ 88,708	$ 88,546	$ 69,348
Average shares outstanding, basic	15,708	15,950	16,081	16,080	16,207	16,271	16,368	16,411	15,975	16,314	15,421
Effect of dilutive securities									20	19	18
Average shares outstanding, diluted	15,733	15,970	16,097	16,101	16,230	16,289	16,386	16,429	15,995	16,333	15,439
Basic earnings per share	$ 1.40	$ 1.25	$ 1.12	$ 1.79	$ 1.38	$ 1.36	$ 1.38	$ 1.31	$ 5.55	$ 5.43	$ 4.50
Diluted earnings per share	$ 1.40	$ 1.25	$ 1.12	$ 1.78	$ 1.38	$ 1.36	$ 1.38	$ 1.30	$ 5.55	$ 5.42	$ 4.49