Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share [Abstract]
Net Income Available to Common Shareholders	$ 22,611	$ 22,371	$ 22,751	$ 21,619	$ 10,713	$ 20,692	$ 20,979	$ 17,616	$ 89,352	$ 70,002	$ 54,310
Undistributed Earnings (Loss) Allocated to Participating Securities, Basic									806	654	591
Distributed earnings allocated to common shares outstanding									35,542	32,483	27,497
Undistributed earnings allocated to common shares outstanding									53,004	36,865	26,222
Net earnings allocated to common shareholders	$ 22,409	$ 22,179	$ 22,554	$ 21,433	$ 10,623	$ 20,491	$ 20,768	$ 17,421	$ 88,546	$ 69,348	$ 53,719
Average shares outstanding, basic	16,207	16,271	16,368	16,411	15,603	15,340	15,326	15,414	16,314	15,421	15,412
Effect of dilutive securities									19	18	24
Average shares outstanding, diluted	16,230	16,289	16,386	16,429	15,618	15,358	15,345	15,436	16,333	15,439	15,436
Basic earnings per share	$ 1.38	$ 1.36	$ 1.38	$ 1.31	$ 0.68	$ 1.34	$ 1.36	$ 1.13	$ 5.43	$ 4.50	$ 3.49
Diluted earnings per share	$ 1.38	$ 1.36	$ 1.38	$ 1.30	$ 0.68	$ 1.33	$ 1.35	$ 1.13	$ 5.42	$ 4.49	$ 3.48