Equity (Details 5) (Stock Options [Member], USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Stock Options [Member]
Equity - Stock-based Compensation Plans [Line Items]
Dividend yield	1.95%	1.65%	2.11%
Risk-free rate of return, Minimum	0.21%	0.29%	0.35%
Risk-free rate of return, Maximum	4.17%	5.51%	5.88%
Expected volatility	35.59%	32.64%	34.41%
Exercise multiple	1.58	1.69	1.75
Post-vesting termination rate	3.14%	3.36%	3.64%
Contractual term (years)	10 years	10 years	10 years
Expected life (years)	7 years	7 years	7 years
Weighted average exercise price of stock options granted	$ 37.91	$ 45.16	$ 35.06
Weighted average fair value of stock options granted	$ 11.33	$ 14.27	$ 11.29