Consolidated Statements Of Changes In Shareholders' Equity (Parenthetical) (USD $)
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Common stock cash dividends, per share $ 0.466 $ 0.417 $ 0.347
Common stock dividend rate 5.00% 5.00% 5.00%
Common stock dividend, shares 275,900 225,937 211,564
Shares under the dividend reinvestment and stock purchase plan 17,749 19,683 23,165
Shares under stock option plan 72,585 65,441 28,264
Shares under employee stock purchase plan 7,710 8,420 10,784
Shares of stock-based compensation awards 9,830 8,480 11,290
Private Placement [Member]      
Shares issued through private placement 650,000