Consolidated Statements of Equity (Parenthetical) - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Dividends declared, per common share	$ 0.645	$ 0.6250	$ 0.5750
Shares issued for acquisitions	0	0	77
Treasury Shares
Purchase of treasury shares			1,193
Additional Paid-in Capital
Income tax on stock option exercise and other shares issued to employees and directors	$ (323)	$ 458	$ 819
Stock option exercises and other shares issued to employees and directors, shares	138	196	187
Retained Earnings
Dividends declared, per common share	$ 0.645	$ 0.6250	$ 0.5750