Share-Based Compensation (Details) - Stock Option Awards - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
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	715
Exercised (in shares)			(476)
Cancelled (in shares)			(15)
Outstanding at the end of the period (in shares)	2,734		2,734
Exercisable at the end of the period (in shares)	1,837		1,837
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)			38.28
Cancelled (in dollars per share)			60.63
Outstanding at the end of the period (in dollars per share)	$ 52.49		52.49
Exercisable at the end of the period (in dollars per share)	$ 44.47		$ 44.47
Share options, aggregate intrinsic value
Options outstanding average remaining contractual life			6 years 1 month 17 days
Options outstanding aggregate intrinsic value	$ 95,205		$ 95,205
Stock options exercisable average remaining contractual life			4 years 11 months 1 day
Stock options exercisable aggregate intrinsic value	78,712		$ 78,712
Additional information pertaining to stock options
Cash received from exercise of stock options			18,000
Unrecognized compensation cost	9,000		$ 9,000
Weighted-average period for amortization of unrecognized compensation cost			1 year 9 months 18 days
Weighted-average grant date fair value of stock options granted (in dollars per share)			$ 16.04	$ 12.99
Total intrinsic value of stock options exercised	$ 10,860	$ 6,416	$ 22,064	$ 21,339