Consolidated Statement of Changes in Shareholders' Equity (Parenthetical) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Stock option exercises/deferred stock unit conversions (shares)	206,336	148,203	820,853
Non-vested stock awards, shares	16,850	22,360	22,360
Purchase of treasury stock, shares	7,960	37,464	18,424
Treasury stock issued/sold to the 401(k) stock purchase plan, shares			40,019
Common stock issued/sold to the 401(k) stock purchase plan, shares		22,680	205,100
Cash dividends, per share	$ 1.90	$ 1.83	$ 1.78