Consolidated Statements of Changes in Stockholders' Equity (Unaudited) (Parentheticals) - $ / shares	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Additional Paid-in Capital [Member]
Restricted stock unit awards vested, shares (in shares)	257,597	284,595
Exercise of stock options, shares (in shares)	600	4,400
Treasury Stock [Member] | Shares Purchased to Fund Options Exercised [Member]
Purchase of treasury shares (in shares)	744,953
Treasury Stock [Member] | Restricted Stock Awards Repurchased to Satisfy Tax Obligations [Member]
Purchase of treasury shares (in shares)	76,212	90,779
Retained Earnings [Member]
Dividends on common stock (in dollars per share)	$ 0.60	$ 0.54
Shares Purchased to Fund Options Exercised [Member]
Purchase of treasury shares (in shares)		10,000
Common shares released from Employee Benefit Trust, shares (in shares)	124,583	114,754