Share-Based Compensation Plans (Details 5) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Stock Option [Member]
Weighted-average assumptions used for options granted
Expected dividends	2.20%	2.20%	3.00%
Expected volatility	40.70%	38.70%	43.90%
Risk-free interest rate	0.60%	1.70%	1.70%
Expected term in years	3 years 8 months 12 days	3 years 7 months 6 days	3 years 4 months 24 days
Grant-date fair value	$ 14.07	$ 12.88	$ 8.93
Employee Stock Purchase Plan [Member]
Weighted-average assumptions used for options granted
Expected dividends	2.70%	2.40%	2.50%
Expected volatility	32.70%	32.80%	35.60%
Risk-free interest rate	0.10%	0.10%	0.20%
Expected term in years	3 months	3 months	3 months
Grant-date fair value	$ 9.53	$ 10.21	$ 8.95