Stock-Based Compensation Plans - Nonqualified Stock Options, Range of Exercise Prices (Details) - Nonqualified Stock Options - $ / shares shares in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Summary of weighted-average remaining contractual lives for stock options outstanding and range of exercise prices
Number of options outstanding (in shares)	6.5	5.3
Weighted-average remaining contractual life for stock options exercisable	6 years 1 month 6 days
Range of exercise prices, Range 1
Summary of weighted-average remaining contractual lives for stock options outstanding and range of exercise prices
Lower limit of exercise price range (in dollars per share)	$ 27.46
Upper limit of exercise price range (in dollars per share)	$ 41.13
Number of options outstanding (in shares)	1.6
Weighted-average remaining contractual life	3 years 3 months 18 days
Range of exercise prices, Range 2
Summary of weighted-average remaining contractual lives for stock options outstanding and range of exercise prices
Lower limit of exercise price range (in dollars per share)	$ 41.14
Upper limit of exercise price range (in dollars per share)	$ 51.53
Number of options outstanding (in shares)	1.0
Weighted-average remaining contractual life	3 years 8 months 12 days
Range of exercise prices, Range 3
Summary of weighted-average remaining contractual lives for stock options outstanding and range of exercise prices
Lower limit of exercise price range (in dollars per share)	$ 51.54
Upper limit of exercise price range (in dollars per share)	$ 52.41
Number of options outstanding (in shares)	1.3
Weighted-average remaining contractual life	9 years 1 month 6 days
Range of exercise prices, Range 4
Summary of weighted-average remaining contractual lives for stock options outstanding and range of exercise prices
Lower limit of exercise price range (in dollars per share)	$ 52.42
Upper limit of exercise price range (in dollars per share)	$ 62.75
Number of options outstanding (in shares)	1.2
Weighted-average remaining contractual life	8 years 1 month 6 days
Range of exercise prices, Range 5
Summary of weighted-average remaining contractual lives for stock options outstanding and range of exercise prices
Lower limit of exercise price range (in dollars per share)	$ 62.76
Upper limit of exercise price range (in dollars per share)	$ 63.98
Number of options outstanding (in shares)	1.4
Weighted-average remaining contractual life	6 years 8 months 12 days
Range of exercise prices, Total Range
Summary of weighted-average remaining contractual lives for stock options outstanding and range of exercise prices
Lower limit of exercise price range (in dollars per share)	$ 27.46
Upper limit of exercise price range (in dollars per share)	$ 63.98
Number of options outstanding (in shares)	6.5