Stock-Based Compensation - Stock Options (Details) - Stock Options - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Stock Option Program
Balance at the beginning of the period	34,569
Granted - Annual	3,457
Exercised	(3,039)
Forfeited	(43)
Balance at the end of the period	34,944
Options exercisable	27,643
Options exercisable, exercise price	$ 134.86
Weighted average exercise price - Beginning balance	138.98
Weighted average exercise price - Granted - Annual	200.80
Weighted average exercise price - Exercised	89.26
Weighted average exercise price - Forfeited	201.03
Weighted average exercise price - Ending balance	$ 149.34
Weighted average remaining contractual life for options outstanding	69 months
Weighted average remaining contractual life for options exercisable	59 months
Aggregate intrinsic value for options outstanding	$ 1,135
Aggregate intrinsic value for options exercisable	$ 1,135
Expiration of annual grants	10 years
Compensation expense yet to be recognized	$ 97
Expense recognition period	23 months
Total intrinsic value of stock options exercised	$ 341	$ 345
Cash received from options exercised	270	212
Tax benefit realized from exercise of stock options	$ 72	$ 73
Share- based compensation assumptions
Weighted average exercise price	$ 201.12
Risk-free interest rate (as a percent)	2.60%
Dividend yield (as a percent)	2.50%
Expected volatility (as a percent)	20.40%
Expected life	79 months
Black-Scholes fair value	$ 34.19
Maximum
Stock Option Program
Vesting period	3 years
Minimum
Stock Option Program
Vesting period	1 year