Consolidated Statements of Changes in Stockholders' Equity (Parentheticals) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Additional Paid-in Capital [Member]
Common shares released from Employee Benefit Trust, shares (in shares)	142,065	147,616	136,559
Restricted stock unit awards vested, shares (in shares)	245,311	204,310	202,466
Exercise of stock options, shares (in shares)	103,530	45,785	150,115
Treasury Stock [Member] | Shares Purchased to Fund Options Exercised [Member]
Purchase of treasury shares (in shares)	403,695	735,599	914,671
Treasury Stock [Member] | Restricted Stock Awards Repurchased to Satisfy Tax Obligations [Member]
Purchase of treasury shares (in shares)	85,982	65,666	59,821
Retained Earnings [Member]
Dividends on common stock (in dollars per share)	$ 0.68	$ 0.64	$ 0.60
Exercise of stock options, shares (in shares)	103,530
Purchase of treasury shares (in shares)	403,695	735,599