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CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (UNAUDITED) (Parenthetical) - $ / shares | 9 Months Ended
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Sep. 30, 2017 | Sep. 30, 2016
Statement of Stockholders' Equity [Abstract] |  |
Cash dividends declared (in dollars per share) | $ 0.78 | $ 0.78
Distribution of shares of treasury stock for directors' compensation (in shares) | 7,880 | 9,532
Distribution of shares of treasury stock for employee stock compensation (in shares) | 5,861 | 7,661
Distribution of shares of treasury stock for directors deferred compensation shares(in shares) | 2,438 | 3,740
Sale of shares of treasury stock (in shares) | 11,688 | 11,857
Restricted stock awards, forfeited (in shares) | 1,139 |

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- Definition Aggregate dividends declared during the period for each share of common stock outstanding. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.3-04) -URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770 + Details
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