Share-Based Compensation (Details) (Stock Option Awards, USD $) Share data in Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Stock Option Awards
Equity stock-based compensation
Term of options	10 years
Period of vesting	3 years
Assumptions used to measure the fair value of awards
Expected life	5 years 6 months	5 years 6 months
Risk-free interest rate (as a percent)	1.36%	1.63%
Expected volatility (as a percent)	25.19%	30.28%
Expected dividend yield (as a percent)	2.04%	2.82%
Stock option activity
Outstanding at the beginning of the period (in shares)	2,889
Granted (in shares)	336	710
Exercised (in shares)	(90)
Cancelled (in shares)	(8)
Outstanding at the end of the period (in shares)	3,127
Exercisable at the end of the period (in shares)	2,210
Share options, weighted average exercise price per share
Outstanding at the beginning of the period (in dollars per share)	$ 46.84
Granted (in dollars per share)	$ 82.28
Exercised (in dollars per share)	$ 41.00
Cancelled (in dollars per share)	$ 60.67
Outstanding at the end of the period (in dollars per share)	$ 50.77
Exercisable at the end of the period (in dollars per share)	$ 43.31
Share options, aggregate intrinsic value
Options outstanding average remaining contractual life	6 years 3 months 29 days
Options outstanding aggregate intrinsic value	$ 86,057,000
Stock options exercisable average remaining contractual life	5 years 3 months
Stock options exercisable aggregate intrinsic value	76,262,000
Additional information pertaining to stock options
Cash received from exercise of stock options	3,000,000
Unrecognized compensation cost	12,000,000
Weighted-average period for amortization of unrecognized compensation cost	2 years 1 month 6 days
Weighted-average grant date fair value of stock options granted (in dollars per share)	$ 16.04	$ 12.97
Total intrinsic value of stock options exercised	$ 3,740,000	$ 2,775,000