Quarterly Unaudited Financial Data (Details) - USD ($) $ / shares in Units, $ 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
Quarterly Unaudited Financial Data [Abstract]
Total Interest Income	$ 39,099	$ 38,810	$ 38,626	$ 37,173	$ 36,799	$ 34,065	$ 32,161	$ 30,428	$ 153,708	$ 133,453	$ 114,612
Total Interest Expense	3,445	3,530	3,253	2,966	2,611	2,157	1,660	1,522	13,194	7,950	6,289
Net Interest Income	35,654	35,280	35,373	34,207	34,188	31,908	30,501	28,906	140,514	125,503	108,323
Provision for Credit Losses	0	0	200	0	2,200	2,500	500	333	200	5,533	2,850
Net Interest Income After Provision for Loan Losses	35,654	35,280	35,173	34,207	31,988	29,408	30,001	28,573	140,314	119,970	105,473
Total Non-Interest Income	4,403	3,974	4,400	4,464	4,063	4,208	2,283	4,665	17,241	15,219	16,762
Total Non-Interest Expense	20,376	20,856	20,565	20,445	18,757	18,621	18,145	19,936	82,242	75,459	67,754
Income Before Income Taxes	19,681	18,398	19,008	18,226	17,294	14,995	14,139	13,302	75,313	59,730	54,481
Provision for Income Taxes	5,037	4,660	4,903	4,677	4,258	2,995	3,589	3,361	19,277	14,203	26,111
Net Income	$ 14,644	$ 13,738	$ 14,105	$ 13,549	$ 13,036	$ 12,000	$ 10,550	$ 9,941	$ 56,036	$ 45,527	$ 28,370
Basic Earnings Per Common Share (in dollars per share)	$ 18.54	$ 17.45	$ 17.92	$ 17.27	$ 16.56	$ 15.12	$ 12.90	$ 12.24	$ 71.18	$ 56.82	$ 35.03