Stockholders' Equity (Details 2) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Stock option activity
Exercised (in shares)	(985,583)	(1,462,369)	(876,115)
Employee stock options, Weighted Average Remaining Contractual Term
Outstanding at the end of the year	6 years 7 months 6 days
Exercisable at the end of the year	6 years 4 months 24 days
Employee stock options, Aggregate Intrinsic Value
Outstanding at the end of the year (in dollars)	$ 208,643
Exercisable at the end of the year (in dollars)	$ 208,559
Stock Options
Stock option activity
Outstanding at the beginning of the period (in shares)	4,054,771
Granted (in shares)	172,250
Exercised (in shares)	(984,583)
Outstanding at the end of the period (in shares)	3,242,438	4,054,771
Exercisable at the end of the year (in shares)	3,070,188
Expected to vest at the end of the year (in shares)	169,737
Employee stock options, Weighted-Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)	$ 76.83
Granted (in dollars per share)	173.25
Exercised (in dollars per share)	39.90
Outstanding at the end of the period (in dollars per share)	93.17	$ 76.83
Exercisable at the end of year (in dollars per share)	88.68
Expected to vest at the end of year (in dollars per share)	$ 173.53
Employee stock options, Weighted Average Remaining Contractual Term
Expected to vest at the end of the year	9 years 6 months
Employee stock options, Aggregate Intrinsic Value
Expected to vest at the end of year (in dollars)	$ 73
Weighted-average fair value of employee stock option granted (in dollars per share)	$ 60.70	$ 40.70	$ 36.10
Total fair value of vested employee options	$ 0	$ 29,500	$ 36,100