Stock-Based Compensation - Stock Options (Details) - Stock Options - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Stock Option Program
Balance at the beginning of the period	33,675
Granted - Annual	4,741
Exercised	(1,639)
Forfeited	(106)
Balance at the end of the period	36,671
Options exercisable	28,682
Options exercisable, exercise price	$ 147.72
Weighted average exercise price - Beginning balance	151.15
Weighted average exercise price - Granted - Annual	157.26
Weighted average exercise price - Exercised	89.34
Weighted average exercise price - Forfeited	185.82
Weighted average exercise price - Ending balance	$ 154.60
Weighted average remaining contractual life for options outstanding	68 months
Weighted average remaining contractual life for options exercisable	56 months
Aggregate intrinsic value for options outstanding	$ 593
Aggregate intrinsic value for options exercisable	$ 593
Expiration of annual grants	10 years
Compensation expense yet to be recognized	$ 89
Expense recognition period	23 months
Total intrinsic value of stock options exercised	$ 127	$ 341
Cash received from options exercised	145	270
Tax benefit realized from exercise of stock options	$ 27	$ 72
Share- based compensation assumptions
Weighted average exercise price	$ 157.24
Risk-free interest rate (as a percent)	1.50%
Dividend yield (as a percent)	2.70%
Expected volatility (as a percent)	19.70%
Expected life	78 months
Black-Scholes fair value	$ 21.58
Maximum
Stock Option Program
Vesting period	3 years
Minimum
Stock Option Program
Vesting period	1 year