Quarterly Results Of Operations (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended									12 Months Ended
	Dec. 31, 2017		Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Results Of Operations [Abstract]
Interest Income	$ 10,339		$ 10,063	$ 9,938	$ 9,546	$ 9,544	$ 9,348	$ 8,988	$ 9,098	$ 39,885	$ 36,979	$ 34,615
Interest Expense	691		629	590	581	589	563	548	545	2,491	2,245	2,371
Net interest income	9,648		9,434	9,348	8,965	8,955	8,785	8,440	8,553	37,394	34,734	32,244
Provision for loan losses	250		250	50	120	450	1,150	1,875	300	670	3,775	1,285
Other noninterest income	3,137		2,970	3,155	2,923	2,984	2,813	2,854	2,981	12,189	11,605	12,652
Securities (losses) gains			1		2	8	(10)	2	(28)	3	22	8
Noninterest expense	18,750	[1]	8,305	8,161	7,957	9,670	7,980	7,730	7,795	43,172	33,175	31,136
Income before income taxes	(6,215)		3,850	4,292	3,813	1,827	2,458	1,691	3,411	5,741	9,389	12,475
Federal income tax expense	1,048	[2]	774	950	793	104	383	130	685	3,565	1,302	2,271
Net income	$ (7,263)		$ 3,076	$ 3,342	$ 3,020	$ 1,723	$ 2,075	$ 1,561	$ 2,726	$ 2,176	$ 8,087	$ 10,204
Basic earnings per share	$ (1.67)		$ 0.71	$ 0.77	$ 0.70	$ 0.40	$ 0.48	$ 0.36	$ 0.64	$ 0.50	$ 1.88	$ 2.40
Diluted earnings per share	(1.67)		0.70	0.77	0.70	0.40	0.48	0.36	0.64	0.50	1.88	2.40
Dividend declared per share	$ 0.24		$ 0.24	$ 0.24	$ 0.21	$ 0.21	$ 0.21	$ 0.21	$ 0.19	$ 0.93	$ 0.82	$ 0.74
Accrued settlement payment	$ 10,000									$ 10,000
Revaluation of deferred tax assets										$ 2,291

[1] Includes $10 million for the accrual of a legal settlement described in Item 3 Legal Proceedings

[2] Includes $2.3 million for revaluation of the net deferred tax assets