Note 14 - Employee Benefits - Stock Options Outstanding by Grant Date (Details) - $ / shares	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Outstanding, shares (in shares)	29,324	31,949	46,451
Outstanding, weighted average exercise price (in dollars per share)	$ 23.67	$ 25.03	$ 27.90
Exercisable, December 31 (in shares)	29,324	31,949
Exercisable, December 31 (in dollars per share)	$ 23.67	$ 25.03
Exercise Price Range 1 [Member]
Exercise price (in dollars per share)	$ 37.48
Outstanding, shares (in shares)	1,337
Outstanding, contractual average life (Year)	131 days
Outstanding, weighted average exercise price (in dollars per share)	$ 37.48
Exercisable, December 31 (in shares)	1,337
Exercisable, December 31 (in dollars per share)	$ 37.48
Exercise Price Range 2 [Member]
Exercise price (in dollars per share)	$ 37
Outstanding, shares (in shares)	1,950
Outstanding, contractual average life (Year)	339 days
Outstanding, weighted average exercise price (in dollars per share)	$ 37
Exercisable, December 31 (in shares)	1,950
Exercisable, December 31 (in dollars per share)	$ 37
Exercise Price Range 3 [Member]
Exercise price (in dollars per share)	$ 36.25
Outstanding, shares (in shares)	1,337
Outstanding, contractual average life (Year)	1 year
Outstanding, weighted average exercise price (in dollars per share)	$ 36.25
Exercisable, December 31 (in shares)	1,337
Exercisable, December 31 (in dollars per share)	$ 36.25
Exercise Price Range 4 [Member]
Exercise price (in dollars per share)	$ 23
Outstanding, shares (in shares)	16,500
Outstanding, contractual average life (Year)	1 year 310 days
Outstanding, weighted average exercise price (in dollars per share)	$ 23
Exercisable, December 31 (in shares)	16,500
Exercisable, December 31 (in dollars per share)	$ 23
Exercise Price Range 5 [Member]
Exercise price (in dollars per share)	$ 17.55
Outstanding, shares (in shares)	8,200
Outstanding, contractual average life (Year)	4 years 127 days
Outstanding, weighted average exercise price (in dollars per share)	$ 17.55
Exercisable, December 31 (in shares)	8,200
Exercisable, December 31 (in dollars per share)	$ 17.55

The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iii)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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Number of options outstanding, including both vested and non-vested options.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(i)-(ii)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

+ 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 (c)(1)(i)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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