Stock-based Compensation Expense - Stock Options Outstanding and Exercisable (Details) shares in Thousands	9 Months Ended
	Sep. 30, 2017 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Exercise price range, options outstanding (in shares) | shares	10,278
Exercise price range, options outstanding, weighted-average remaining contractual life (in years)	7 years 2 months 19 days
Exercise price range, options outstanding, weighted-average exercise price (in dollars per share)	$ 91.28
Exercise price range, options exercisable (in shares) | shares	5,162
Exercise price range, options exercisable, weighted-average exercise price (in dollars per share)	$ 77.92
$18.93–$20.00
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Exercise price, low end of range (in dollars per share)	18.93
Exercise price, high end of range (in dollars per share)	$ 20.00
Exercise price range, options outstanding (in shares) | shares	128
Exercise price range, options outstanding, weighted-average remaining contractual life (in years)	4 months 6 days
Exercise price range, options outstanding, weighted-average exercise price (in dollars per share)	$ 18.93
Exercise price range, options exercisable (in shares) | shares	128
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, Options, Additional Disclosures [Abstract]
Exercise price, low end of range (in dollars per share)	20.01
Exercise price, high end of range (in dollars per share)	$ 40
Exercise price range, options outstanding (in shares) | shares	834
Exercise price range, options outstanding, weighted-average remaining contractual life (in years)	2 years 2 months 16 days
Exercise price range, options outstanding, weighted-average exercise price (in dollars per share)	$ 34.51
Exercise price range, options exercisable (in shares) | shares	834
Exercise price range, options exercisable, weighted-average exercise price (in dollars per share)	$ 34.51
$40.01–$60.00
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Exercise price, low end of range (in dollars per share)	40.01
Exercise price, high end of range (in dollars per share)	$ 60
Exercise price range, options outstanding (in shares) | shares	877
Exercise price range, options outstanding, weighted-average remaining contractual life (in years)	4 years 9 months 29 days
Exercise price range, options outstanding, weighted-average exercise price (in dollars per share)	$ 49.17
Exercise price range, options exercisable (in shares) | shares	877
Exercise price range, options exercisable, weighted-average exercise price (in dollars per share)	$ 49.17
$60.01–$80.00
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Exercise price, low end of range (in dollars per share)	60.01
Exercise price, high end of range (in dollars per share)	$ 80
Exercise price range, options outstanding (in shares) | shares	821
Exercise price range, options outstanding, weighted-average remaining contractual life (in years)	6 years 5 months 16 days
Exercise price range, options outstanding, weighted-average exercise price (in dollars per share)	$ 75.62
Exercise price range, options exercisable (in shares) | shares	649
Exercise price range, options exercisable, weighted-average exercise price (in dollars per share)	$ 75.44
$80.01–$100.00
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Exercise price, low end of range (in dollars per share)	80.01
Exercise price, high end of range (in dollars per share)	$ 100
Exercise price range, options outstanding (in shares) | shares	4,587
Exercise price range, options outstanding, weighted-average remaining contractual life (in years)	8 years 3 months 29 days
Exercise price range, options outstanding, weighted-average exercise price (in dollars per share)	$ 89.37
Exercise price range, options exercisable (in shares) | shares	1,397
Exercise price range, options exercisable, weighted-average exercise price (in dollars per share)	$ 89.47
$100.01–$120.00
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Exercise price, low end of range (in dollars per share)	100.01
Exercise price, high end of range (in dollars per share)	$ 120
Exercise price range, options outstanding (in shares) | shares	1,137
Exercise price range, options outstanding, weighted-average remaining contractual life (in years)	7 years 4 months 10 days
Exercise price range, options outstanding, weighted-average exercise price (in dollars per share)	$ 109.34
Exercise price range, options exercisable (in shares) | shares	586
Exercise price range, options exercisable, weighted-average exercise price (in dollars per share)	$ 109.24
$120.01–$140.00
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Exercise price, low end of range (in dollars per share)	120.01
Exercise price, high end of range (in dollars per share)	$ 140.00
Exercise price range, options outstanding (in shares) | shares	1,260
Exercise price range, options outstanding, weighted-average remaining contractual life (in years)	7 years 10 months 17 days
Exercise price range, options outstanding, weighted-average exercise price (in dollars per share)	$ 130.24
Exercise price range, options exercisable (in shares) | shares	688
Exercise price range, options exercisable, weighted-average exercise price (in dollars per share)	$ 129.86
$140.01–$160.00
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Exercise price, low end of range (in dollars per share)	140.01
Exercise price, high end of range (in dollars per share)	$ 160.00
Exercise price range, options outstanding (in shares) | shares	0
Exercise price range, options outstanding, weighted-average remaining contractual life (in years)	0 days
Exercise price range, options outstanding, weighted-average exercise price (in dollars per share)	$ 0.00
Exercise price range, options exercisable (in shares) | shares	0
Exercise price range, options exercisable, weighted-average exercise price (in dollars per share)	$ 0.00
$160.01–$163.74
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Exercise price, low end of range (in dollars per share)	160.01
Exercise price, high end of range (in dollars per share)	$ 163.74
Exercise price range, options outstanding (in shares) | shares	634
Exercise price range, options outstanding, weighted-average remaining contractual life (in years)	9 years 9 months 18 days
Exercise price range, options outstanding, weighted-average exercise price (in dollars per share)	$ 162.94
Exercise price range, options exercisable (in shares) | shares	3
Exercise price range, options exercisable, weighted-average exercise price (in dollars per share)	$ 162.94