Consolidated Statement of Changes in Stockholders' Equity (Parentheticals) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Treasury Stock [Member]
Purchase of treasury stock (in shares)			196,635
Retained Earnings [Member]
Cash dividends per share (in dollars per share)	$ 1.08	$ 1.08	$ 1.07
Common Stock [Member]
Common stock, issuance cost	$ 760	$ 697
Cash dividends per share (in dollars per share)	$ 1.08	$ 1.08	$ 1.07

Amount of decrease in additional paid in capital (APIC) resulting from direct costs associated with issuing stock. Includes, but is not limited to, legal and accounting fees and direct costs associated with stock issues under a shelf registration.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=84159872&loc=d3e21463-112644

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
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-Subparagraph (SX 210.3-04)
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-Paragraph 1
-Subparagraph (SX 210.5-02(29))
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-Section 50
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