Condensed Consolidated Statements of Equity (Parenthetical) (Unaudited) - USD ($) shares in Thousands, $ in Thousands	9 Months Ended
Sep. 30, 2017	Sep. 30, 2016
Dividends declared, per common share	$ 0.48	$ 0.465
Additional Paid-in Capital
Income tax on stock option exercise and other shares issued to employees and directors	$ (323)	$ 471
Stock option exercises and other shares issued to employees and directors, shares	122	202
Retained Earnings
Dividends declared, per common share	$ 0.48	$ 0.465

The tax effects of employee stock option transactions that are recognized differently for financial reporting and tax purposes, occurring during the period and charged or credited directly to shareholders' equity.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 740
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=79981250&loc=d3e23586-113945

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 740
-Section 45
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=79981250&loc=d3e23594-113945

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 20
-Section 45
-Paragraph 11
-Subparagraph (d)
-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