CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (Parenthetical) - $ / shares	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 09, 2015
Shares authorized for issuance of grants under equity compensation plan (in shares)				331,500
Common Stock [Member] \| Common Shares Class A Non-Voting [Member]
Common stock, par value (in dollars per share)	$ 1.00
Common stock, shares authorized (in shares)	15,000,000	15,000,000	15,000,000
Common Stock Shares Issued (in shares)	8,362,431	8,275,010	8,205,190
Shares available for purchase through retirement plans (in shares)	500,000
Shares authorized for issuance of grants under equity compensation plan (in shares)				331,500
Common Stock [Member] \| Common Shares Class B Voting [Member]
Common stock, par value (in dollars per share)	$ 1.00
Common stock, shares authorized (in shares)	1,040,000	1,040,000	1,040,000
Common Stock Shares Issued (in shares)	882,000	882,000	882,000

Face amount or stated value per share of common stock.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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The maximum number of common shares permitted to be issued by an entity's charter and bylaws.

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Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury.

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The shares or units in an ESOP trust that have been assigned to individual participant accounts based on a known formula. IRS rules require allocations to be nondiscriminatory generally based on compensation, length of service, or a combination of both. For any particular participant such shares or units may be vested, unvested, or partially vested.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 40
-Section 50
-Paragraph 1
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=65895303&loc=d3e17540-113929

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The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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