Stock-Based Compensation - Exercise Price for Stock Options Outstanding and Exercisable (Details) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Exercise prices for stock options outstanding and exercisable
Number of stock options outstanding (in shares)	17,403,339
Options Outstanding, Weighted-Average Exercise Price (in dollars per share)	$ 32.59
Stock options
Exercise prices for stock options outstanding and exercisable
Exercise prices, outstanding stock option awards, low end of range (in dollars per share)	10.01
Exercise prices, outstanding stock option awards, high end of range (in dollars per share)	$ 70.00
Number of stock options outstanding (in shares)	27,248,662	13,715,612	14,202,039	8,847,734
Options Outstanding, Weighted-Average Remaining Contractual Life	8 years 3 months 7 days
Options Outstanding, Weighted-Average Exercise Price (in dollars per share)	$ 34.85	$ 41.71	$ 42.08	$ 43.90
Number of stock options exercisable	5,193,238	2,507,834	1,781,153
Options Exercisable, Weighted-Average Remaining Contractual Life	5 years 10 months 24 days
Options Exercisable, Weighted-Average Exercise Price (in dollars per share)	$ 40.21	$ 44.93	$ 41.41
Stock options | Range Of Exercise Prices $10.01 - $20.00
Exercise prices for stock options outstanding and exercisable
Exercise prices, outstanding stock option awards, low end of range (in dollars per share)	10.01
Exercise prices, outstanding stock option awards, high end of range (in dollars per share)	$ 20.00
Number of stock options outstanding (in shares)	244,500
Options Outstanding, Weighted-Average Remaining Contractual Life	8 years 3 months 18 days
Options Outstanding, Weighted-Average Exercise Price (in dollars per share)	$ 18.70
Number of stock options exercisable	8,336
Options Exercisable, Weighted-Average Remaining Contractual Life	7 years 9 months
Options Exercisable, Weighted-Average Exercise Price (in dollars per share)	$ 18.70
Stock options | Range of Exercise Prices $20.01 - $30.00
Exercise prices for stock options outstanding and exercisable
Exercise prices, outstanding stock option awards, low end of range (in dollars per share)	20.01
Exercise prices, outstanding stock option awards, high end of range (in dollars per share)	$ 30.00
Number of stock options outstanding (in shares)	13,563,775
Options Outstanding, Weighted-Average Remaining Contractual Life	9 years 7 months 17 days
Options Outstanding, Weighted-Average Exercise Price (in dollars per share)	$ 27.68
Number of stock options exercisable	694,722
Options Exercisable, Weighted-Average Remaining Contractual Life	1 year 7 months 6 days
Options Exercisable, Weighted-Average Exercise Price (in dollars per share)	$ 27.17
Stock options | Range of Exercise Prices $30.01 - $40.00
Exercise prices for stock options outstanding and exercisable
Exercise prices, outstanding stock option awards, low end of range (in dollars per share)	30.01
Exercise prices, outstanding stock option awards, high end of range (in dollars per share)	$ 40.00
Number of stock options outstanding (in shares)	8,911,281
Options Outstanding, Weighted-Average Remaining Contractual Life	7 years 5 months 8 days
Options Outstanding, Weighted-Average Exercise Price (in dollars per share)	$ 35.49
Number of stock options exercisable	2,930,928
Options Exercisable, Weighted-Average Remaining Contractual Life	7 years 1 month 20 days
Options Exercisable, Weighted-Average Exercise Price (in dollars per share)	$ 35.49
Stock options | Range of Exercise Prices $40.01 - $50.00
Exercise prices for stock options outstanding and exercisable
Exercise prices, outstanding stock option awards, low end of range (in dollars per share)	40.01
Exercise prices, outstanding stock option awards, high end of range (in dollars per share)	$ 50.00
Number of stock options outstanding (in shares)	1,436,028
Options Outstanding, Weighted-Average Remaining Contractual Life	6 years 6 months 18 days
Options Outstanding, Weighted-Average Exercise Price (in dollars per share)	$ 47.48
Number of stock options exercisable	659,500
Options Exercisable, Weighted-Average Remaining Contractual Life	6 years 3 months 18 days
Options Exercisable, Weighted-Average Exercise Price (in dollars per share)	$ 47.30
Stock options | Range of Exercise Prices $50.01 - $60.00
Exercise prices for stock options outstanding and exercisable
Exercise prices, outstanding stock option awards, low end of range (in dollars per share)	50.01
Exercise prices, outstanding stock option awards, high end of range (in dollars per share)	$ 60.00
Number of stock options outstanding (in shares)	2,034,878
Options Outstanding, Weighted-Average Remaining Contractual Life	5 years 5 months 26 days
Options Outstanding, Weighted-Average Exercise Price (in dollars per share)	$ 57.53
Number of stock options exercisable	488,752
Options Exercisable, Weighted-Average Remaining Contractual Life	4 years 8 months 23 days
Options Exercisable, Weighted-Average Exercise Price (in dollars per share)	$ 56.88
Stock options | Range of Exercise Prices $60.01 - $70.00
Exercise prices for stock options outstanding and exercisable
Exercise prices, outstanding stock option awards, low end of range (in dollars per share)	60.01
Exercise prices, outstanding stock option awards, high end of range (in dollars per share)	$ 70.00
Number of stock options outstanding (in shares)	1,058,200
Options Outstanding, Weighted-Average Remaining Contractual Life	5 years 4 months 28 days
Options Outstanding, Weighted-Average Exercise Price (in dollars per share)	$ 64.24
Number of stock options exercisable	411,000
Options Exercisable, Weighted-Average Remaining Contractual Life	5 years 25 days
Options Exercisable, Weighted-Average Exercise Price (in dollars per share)	$ 65.18