Stock-based Compensation Expense - Stock Options Outstanding and Exercisable (Details) shares in Thousands	6 Months Ended
	Jun. 30, 2016 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award
Exercise price range, options outstanding (in shares) | shares	12,231
Exercise price range, options outstanding, weighted-average remaining contractual life (in years)	7 years 2 months 16 days
Exercise price range, options outstanding, weighted-average exercise price (in dollars per share)	$ 79.37
Exercise price range, options exercisable (in shares) | shares	6,490
Exercise price range, options exercisable, weighted-average exercise price (in dollars per share)	$ 63.32
$18.93–$20.00
Share-based Compensation Arrangement by Share-based Payment Award
Exercise price, low end of range (usd per share)	18.93
Exercise price, high end of range (usd per share)	$ 20.00
Exercise price range, options outstanding (in shares) | shares	137
Exercise price range, options outstanding, weighted-average remaining contractual life (in years)	1 year 7 months 10 days
Exercise price range, options outstanding, weighted-average exercise price (in dollars per share)	$ 18.93
Exercise price range, options exercisable (in shares) | shares	137
Exercise price range, options exercisable, weighted-average exercise price (in dollars per share)	$ 18.93
$20.01–$40.00
Share-based Compensation Arrangement by Share-based Payment Award
Exercise price, low end of range (usd per share)	20.01
Exercise price, high end of range (usd per share)	$ 40
Exercise price range, options outstanding (in shares) | shares	1,964
Exercise price range, options outstanding, weighted-average remaining contractual life (in years)	3 years 5 months 12 days
Exercise price range, options outstanding, weighted-average exercise price (in dollars per share)	$ 34.24
Exercise price range, options exercisable (in shares) | shares	1,962
Exercise price range, options exercisable, weighted-average exercise price (in dollars per share)	$ 34.23
$40.01–$60.00
Share-based Compensation Arrangement by Share-based Payment Award
Exercise price, low end of range (usd per share)	40.01
Exercise price, high end of range (usd per share)	$ 60
Exercise price range, options outstanding (in shares) | shares	2,066
Exercise price range, options outstanding, weighted-average remaining contractual life (in years)	6 years 26 days
Exercise price range, options outstanding, weighted-average exercise price (in dollars per share)	$ 48.14
Exercise price range, options exercisable (in shares) | shares	1,657
Exercise price range, options exercisable, weighted-average exercise price (in dollars per share)	$ 48.66
$60.01–$80.00
Share-based Compensation Arrangement by Share-based Payment Award
Exercise price, low end of range (usd per share)	60.01
Exercise price, high end of range (usd per share)	$ 80
Exercise price range, options outstanding (in shares) | shares	1,368
Exercise price range, options outstanding, weighted-average remaining contractual life (in years)	7 years 7 months 13 days
Exercise price range, options outstanding, weighted-average exercise price (in dollars per share)	$ 75.90
Exercise price range, options exercisable (in shares) | shares	734
Exercise price range, options exercisable, weighted-average exercise price (in dollars per share)	$ 75.39
$80.01–$100.00
Share-based Compensation Arrangement by Share-based Payment Award
Exercise price, low end of range (usd per share)	80.01
Exercise price, high end of range (usd per share)	$ 100
Exercise price range, options outstanding (in shares) | shares	3,555
Exercise price range, options outstanding, weighted-average remaining contractual life (in years)	8 years 7 months 6 days
Exercise price range, options outstanding, weighted-average exercise price (in dollars per share)	$ 90.68
Exercise price range, options exercisable (in shares) | shares	1,080
Exercise price range, options exercisable, weighted-average exercise price (in dollars per share)	$ 88.91
$100.01–$120.00
Share-based Compensation Arrangement by Share-based Payment Award
Exercise price, low end of range (usd per share)	100.01
Exercise price, high end of range (usd per share)	$ 120
Exercise price range, options outstanding (in shares) | shares	1,644
Exercise price range, options outstanding, weighted-average remaining contractual life (in years)	8 years 6 months 26 days
Exercise price range, options outstanding, weighted-average exercise price (in dollars per share)	$ 109.32
Exercise price range, options exercisable (in shares) | shares	500
Exercise price range, options exercisable, weighted-average exercise price (in dollars per share)	$ 109.27
$120.01–$134.69
Share-based Compensation Arrangement by Share-based Payment Award
Exercise price, low end of range (usd per share)	120.01
Exercise price, high end of range (usd per share)	$ 134.69
Exercise price range, options outstanding (in shares) | shares	1,497
Exercise price range, options outstanding, weighted-average remaining contractual life (in years)	9 years 18 days
Exercise price range, options outstanding, weighted-average exercise price (in dollars per share)	$ 130.61
Exercise price range, options exercisable (in shares) | shares	420
Exercise price range, options exercisable, weighted-average exercise price (in dollars per share)	$ 129.84