Loans (Impaired Financing Receivables) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Unpaid contractual principal balance	$ 36,063	$ 32,987	$ 36,063	$ 32,987	$ 43,618
Recorded investment with no allowance	32,701	26,264	32,701	26,264	39,028
Recorded investment with allowance	2,847	6,436	2,847	6,436	4,226
Total recorded investment	35,548	32,700	35,548	32,700	43,254
Related allowance	1,010	818	1,010	818	1,024
Average recorded investment	35,657	32,884	35,951	33,214	44,159
Interest income recognized	438	395	1,062	1,045	1,829
Commercial Real Estate Loans [Member]
Unpaid contractual principal balance	26,588	24,233	26,588	24,233	33,180
Recorded investment with no allowance	24,664	19,824	24,664	19,824	30,921
Recorded investment with allowance	1,561	4,211	1,561	4,211	2,008
Total recorded investment	26,225	24,035	26,225	24,035	32,929
Related allowance	174	155	174	155	370
Average recorded investment	26,297	24,153	26,499	24,399	33,575
Interest income recognized	340	319	763	799	1,379
Residential First Mortgage Loans [Member]
Unpaid contractual principal balance	2,655	2,277	2,655	2,277	2,455
Recorded investment with no allowance	2,616	1,808	2,616	1,808	1,978
Recorded investment with allowance		463		463	459
Total recorded investment	2,616	2,271	2,616	2,271	2,437
Related allowance		7		7	2
Average recorded investment	2,627	2,284	2,651	2,302	2,479
Interest income recognized	31	18	90	67	91
Residential Rentals Loans [Member]
Unpaid contractual principal balance	1,431	2,669	1,431	2,669	2,389
Recorded investment with no allowance	1,377	2,271	1,377	2,271	1,981
Recorded investment with allowance		397		397	395
Total recorded investment	1,377	2,668	1,377	2,668	2,376
Related allowance		21		21	18
Average recorded investment	1,382	2,673	1,400	2,711	2,432
Interest income recognized	11	22	47	77	111
Construction And Land Development Loans [Member]
Unpaid contractual principal balance	729	729	729	729	729
Recorded investment with no allowance	729		729
Recorded investment with allowance		729		729	729
Total recorded investment	729	729	729	729	729
Related allowance		163		163	163
Average recorded investment	729	729	729	729	729
Interest income recognized	11	9	30	16	26
Home Equity And Second Mortgage Loans [Member]
Unpaid contractual principal balance	298	225	298	225	317
Recorded investment with no allowance	293	225	293	225	317
Total recorded investment	293	225	293	225	317
Average recorded investment	300	225	304	226	318
Interest income recognized	4	2	10	5	12
Commercial Loans [Member]
Unpaid contractual principal balance	2,784	2,324	2,784	2,324	3,010
Recorded investment with no allowance	1,890	2,096	1,890	2,096	2,783
Recorded investment with allowance	883	169	883	169	168
Total recorded investment	2,773	2,265	2,773	2,265	2,951
Related allowance	458	169	458	169	168
Average recorded investment	2,775	2,298	2,779	2,317	3,048
Interest income recognized	38	24	89	71	137
Consumer Loans [Member]
Unpaid contractual principal balance	1		1
Recorded investment with allowance	1		1
Total recorded investment	1		1
Related allowance	1		1
Average recorded investment	1		1
Commercial Equipment Loans [Member]
Unpaid contractual principal balance	1,577	530	1,577	530	1,538
Recorded investment with no allowance	1,132	40	1,132	40	1,048
Recorded investment with allowance	402	467	402	467	467
Total recorded investment	1,534	507	1,534	507	1,515
Related allowance	377	303	377	303	303
Average recorded investment	1,546	522	1,588	530	1,578
Interest income recognized	$ 3	$ 1	$ 33	$ 10	$ 73

Average amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5212-111524

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5258-111524

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 14A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953550-111524

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