Stock Options and Incentive Plans (Schedule of Weighted Average Exercise Price) (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Weighted average exercise price
Shares under option January 1	$ 19.54	$ 19.51	$ 19.5
Options granted
Options canceled	$ 21.23	$ 20.54	$ 21.98
Options exercised	$ 19.65	$ 19.03	$ 17.66
Shares under option December 31	$ 19.45	$ 19.54	$ 19.51
Options exercisable December 31	$ 19.45	$ 19.54	$ 19.51