Share Tracking Award Plans (Details) - Share tracking award plans (STAP) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Awards granted under the STAP
Grant expiration period from the grant date	10 years
Share-based awards, vesting period	4 years
Aggregate STAP liability	$ 354,800	$ 322,700
Long term portion of STAP liability	$ 80,200	$ 40,600
Expected volatility maximum period	5 years
Assumptions used to measure the fair value of STAP awards
Expected volatility (as a percent)	35.30%	34.00%	32.70%
Risk-free interest rate (as a percent)	1.40%	1.30%	1.10%
Expected term of awards	3 years 4 months 24 days	4 years	3 years 10 months 24 days
Expected forfeiture rate (as a percent)	8.80%	9.30%	10.10%
Expected dividend yield (as a percent)	0.00%	0.00%	0.00%
Share-based awards activity
Outstanding at the beginning of the year (in shares)	7,716,424
Granted (in shares)	1,655,388
Exercised (in shares)	(2,281,711)
Forfeited (in shares)	(244,938)
Outstanding at the end of the year (in shares)	6,845,163	7,716,424
Exercisable at the end of the year (in shares)	2,115,571
Expected to vest at the end of the year (in shares)	4,306,092
Share awards, Weighted-Average Exercise Price
Outstanding at the beginning of the year (in dollars per share)	$ 62.59
Granted (in dollars per share)	159.68
Exercised (in dollars per share)	56.71
Forfeited (in dollars per share)	95.37
Outstanding at the end of the year (in dollars per share)	86.86	$ 62.59
Exercisable at the end of the year (in dollars per share)	67.79
Expected to vest at the end of the year (in dollars per share)	$ 95.34
Share awards, Weighted Average Remaining Contractual Term
Outstanding at the end the year	7 years 3 months 18 days
Exercisable at the end of the year	6 years 1 month 6 days
Expected to vest at the end of the year	7 years 10 months 24 days
Share awards, Aggregate Intrinsic Value
Outstanding at the end of the year (in dollars)	$ 487,010
Exercisable at the end of the year (in dollars)	188,683
Expected to vest at the end of the year (in dollars)	$ 271,767
Awards granted during the period, weighted average grant date fair value (in dollars per share)	$ 58.52	$ 33.82	$ 24.78