Stockholders' Equity (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Stock option activity
Exercised (in shares)	(876,115)	(575,944)	(837,690)
Stock Options
Stock option activity
Outstanding at the beginning of the period (in shares)	4,551,050
Granted (in shares)	1,000,000
Exercised (in shares)	(797,613)
Forfeited (in shares)	(3,988)
Outstanding at the end of the period (in shares)	4,749,449	4,551,050
Employee stock options, Weighted-Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)	$ 38.95
Granted (in dollars per share)	$ 113.08
Exercised (in dollars per share)	$ 30.12
Forfeited (in dollars per share)	$ 10.48
Outstanding at the end of the period (in dollars per share)	$ 56.06	$ 38.95
Employee stock options, Weighted Average Remaining Contractual Term
Outstanding at the end the period	5 years 8 months 12 days
Employee stock options, Aggregate Intrinsic Value
Outstanding at the end of the period (in dollars)	$ 270,801,000
Weighted-average fair value of employee stock option granted (in dollars per share)	$ 36.10	$ 19.74	$ 0.00
Total fair value of vested employee options	$ 36,100,000	$ 3,000,000	$ 1,600,000