CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (Parenthetical) - $ / shares
 3 Months Ended
Mar. 31, 2016
Mar. 31, 2015
Statement of Stockholders' Equity [Abstract]    
Issuance of common shares under stock based compensation awards, including related tax effects 91,340 94,361 [1]
Common stock acquired for treasury 269,667 104,661 [1]
Common stock dividend (in dollars per share) $ 0.18 $ 0.164 [2]
[1] *Share and per share data gives retrospective recognition to a 10% stock dividend declared on July 22, 2015 and issued on August 14, 2015.
[2] *The computation of three months ended March 31, 2015 per common share data and shares outstanding gives retrospective recognition to a 10% stock dividend declared on July 22, 2015 and issued on August 14, 2015.