Equity (Weighted Average Assumptions Used to Determine Fair Value of Stock Options) (Details) - Stock Options	12 Months Ended
	Dec. 31, 2017 $ / shares	Dec. 31, 2016 $ / shares	Dec. 31, 2015 $ / shares
Equity - Stock-based Compensation Plans [Line Items]
Dividend yield	3.05%	3.90%	2.72%
Risk-free rate of return, Minimum	0.94%	0.62%	0.20%
Risk-free rate of return, Maximum	3.22%	2.85%	3.04%
Expected volatility	34.19%	33.58%	32.56%
Exercise multiple	1.43	1.43	1.44
Post-vesting termination rate	2.94%	2.58%	2.73%
Contractual term (years)	10 years	10 years	10 years
Expected life (years)	6 years	7 years	7 years
Weighted average exercise price of stock options granted	$ 46.85	$ 34.33	$ 45.91
Weighted average fair value of stock options granted	$ 12.36	$ 8.27	$ 11.87