Share Tracking Award Plans (Details) (Share Tracking Awards Plan [Member], USD $)	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Share Tracking Awards Plan [Member]
Awards granted under the STAP
Share-based awards, vesting period	4 years
Grant expiration period from the grant date	10 years
Aggregate STAP liability	$ 336,800,000		$ 305,200,000
Long term portion of STAP liability	34,900,000		17,200,000
Assumptions used to measure the fair value of STAP awards
Expected volatility (as a percent)	34.90%	34.20%
Risk-free interest rate (as a percent)	1.30%	1.10%
Expected term of awards	3 years 10 months 24 days	4 years 1 month 6 days
Expected forfeiture rate (as a percent)	9.90%	9.40%
Expected dividend yield (as a percent)	0.00%	0.00%
Share-based awards activity
Outstanding at the beginning of the period (in shares)	8,734,901
Granted (in shares)	1,564,650
Exercised (in shares)	(1,987,179)
Forfeited (in shares)	(220,811)
Outstanding at the end of the period (in shares)	8,091,561
Exercisable at the end of the period (in shares)	2,939,094
Expected to vest at the end of the period (in shares)	4,636,133
Share awards, Weighted-Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)	$ 52.75
Granted (in dollars per share)	$ 94.65
Exercised (in dollars per share)	$ 48.23
Forfeited (in dollars per share)	$ 62.71
Outstanding at the end of the period (in dollars per share)	$ 61.69
Exercisable at the end of the period (in dollars per share)	$ 52.02
Expected to vest at the end of the period (in dollars per share)	$ 67.46
Share awards, Weighted Average Remaining Contractual Term
Outstanding at the end the period	7 years 7 months 6 days
Exercisable at the end of the period	6 years 1 month 6 days
Expected to vest at the end of the period	8 years 6 months
Share awards, Aggregate Intrinsic Value
Outstanding at the end of the period (in dollars)	541,821,000
Exercisable at the end of the period (in dollars)	225,237,000
Expected to vest at the end of the period (in dollars)	$ 283,676,000
Awards granted during the period, weighted average grant date fair value (in dollars per share)	$ 33.61	$ 24.70