Investment Securities (Narrative) (Details)	9 Months Ended
Sep. 30, 2017 USD ($) security	Dec. 31, 2016 USD ($)
Schedule of Available for Sale Securities and Held to Maturity Securities [Line Items]
Investment in Federal Home Loan and Atlantic Central Bankers Bank stock recorded at cost	$ 991,000	$ 1,600,000
Investment securities pledged to secure securities sold under repurchase agreements	0	0
Investment securities pledged to secure a line of credit with the FHLB and a letter of credit with that institution, fair value	606,800,000	607,200,000
Other than temporary impairment charges	0
Amortized cost of securities	$ 86,402,000	93,467,000
Held-to-maturity [Member]
Schedule of Available for Sale Securities and Held to Maturity Securities [Line Items]
Number of securities secured by diversified portfolios of corporate securities \| security	3
Number of single issuer trust preferred securities \| security	2
Single Issuers [Member]
Schedule of Available for Sale Securities and Held to Maturity Securities [Line Items]
Number of single issuer trust preferred securities \| security	2
Amortized cost of securities	$ 11,017,000	17,983,000
Bank And Insurance Issuers [Member]
Schedule of Available for Sale Securities and Held to Maturity Securities [Line Items]
Amortized cost of securities	$ 11,000,000
Bank Issuers [Member]
Schedule of Available for Sale Securities and Held to Maturity Securities [Line Items]
Number of bank senior notes \| security	1
Amortized cost of securities	$ 1,900,000
Insurance Issuers [Member]
Schedule of Available for Sale Securities and Held to Maturity Securities [Line Items]
Number of securities issued by an insurance company \| security	1
Amortized cost of securities	$ 9,100,000
Pooled [Member]
Schedule of Available for Sale Securities and Held to Maturity Securities [Line Items]
Amortized cost of securities	$ 75,385,000	$ 75,484,000

Number Of Bank Senior Notes

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Number Of Securities Issued By An Insurance Company

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Number Of Securities Secured By Diversified Portfolios Of Corporate Securities

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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This item represents an other than temporary decline in value that has been recognized against an investment accounted for under the cost method of accounting. The excess of the carrying amount over the fair value of the investment represents the amount of the write down which is or was reflected in earnings. The written down value is a new cost basis with the adjusted value of the investment becoming its new carrying value. Evidence of a loss in value might include, but would not necessarily be limited to, absence of an ability to recover the carrying amount of the investment or inability of the investee to sustain an earnings capacity which would justify the carrying amount of the investment.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 325
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=75025870&loc=d3e40691-111596

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Federal Home Loan Bank (FHLB) stock represents an equity interest in a FHLB. It does not have a readily determinable fair value because its ownership is restricted and it lacks a market (liquidity).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 325
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=75031641&loc=d3e63345-112809

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Amount before other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.

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The fair value, as of the date of each statement of financial position presented, of securities which are owned but transferred to serve as collateral for the payment of the FHLB debt obligations, and that are reclassified and separately reported in the statement of financial position because the transferee has the right by contract or custom to sell or re-pledge them.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=66007379&loc=d3e113888-111728

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The fair value, as of the date of each statement of financial position presented, of securities which are owned but transferred to serve as collateral for the payment of repurchase agreements, and that are reclassified and separately reported in the statement of financial position because the transferee has the right by contract or custom to sell or re-pledge them.

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