Consolidated Statements of Changes in Stockholders' Equity (Unaudited) (Parentheticals) - USD ($)	9 Months Ended
Sep. 30, 2017	Sep. 30, 2016
Retained Earnings [Member]
Dividends, per share (in dollars per share)	$ 0.56	$ 0.55
AOCI Attributable to Parent [Member]
Other comprehensive income (loss), tax	$ 1,234,000	$ 2,361,000
Dividends, per share (in dollars per share)	$ 0.56	$ 0.55
Other comprehensive income (loss), tax	$ 1,234,000	$ 2,361,000

Amount of tax expense (benefit) allocated to other comprehensive income (loss).

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=84228862&loc=d3e640-108580

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 20
-Section 45
-Paragraph 11
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=79507043&loc=d3e39076-109324

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration