Stock-Based Compensation - Stock Options (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Stock Option Program
Balance at the beginning of the period	34,569	34,965
Balance at the end of the period		34,569	34,965
Weighted average exercise price - Beginning balance	$ 138.98	$ 125.73
Weighted average exercise price - Ending balance		138.98	$ 125.73
Share- based compensation assumptions
Weighted average exercise price	$ 201.12	$ 233.63	$ 175.76
Risk-free interest rate (as a percent)	2.60%	2.70%	2.10%
Dividend yield (as a percent)	2.50%	2.40%	2.50%
Expected volatility (as a percent)	20.40%	21.00%	17.30%
Expected life	79 months	78 months	78 months
Black-Scholes fair value	$ 34.19	$ 41.59	$ 23.51
Stock Options
Stock Option Program
Balance at the beginning of the period	34,569	34,965	36,196
Granted - Annual	3,434	3,211	5,410
Exercised	(4,193)	(3,482)	(6,474)
Forfeited	(135)	(125)	(167)
Balance at the end of the period	33,675	34,569	34,965
Options exercisable	26,487	26,117	24,281
Options exercisable, exercise price	$ 136.75	$ 121.98	$ 108.50
Weighted average exercise price - Beginning balance	138.98	125.73	112.07
Weighted average exercise price - Granted - Annual	200.80	233.19	175.93
Weighted average exercise price - Exercised	89.89	91.01	90.37
Weighted average exercise price - Forfeited	201.27	188.00	162.36
Weighted average exercise price - Ending balance	$ 151.15	$ 138.98	$ 125.73
Weighted average remaining contractual life for options outstanding	64 months
Weighted average remaining contractual life for options exercisable	54 months
Aggregate intrinsic value for options outstanding	$ 1,100
Aggregate intrinsic value for options exercisable	$ 1,100
Expiration of annual grants	10 years
Compensation expense yet to be recognized	$ 62
Expense recognition period	20 months
Total intrinsic value of stock options exercised	$ 433	$ 469	$ 703
Cash received from options exercised	375	316	585
Tax benefit realized from exercise of stock options	$ 91	$ 99	$ 238
Stock Options | Maximum
Stock Option Program
Vesting period	3 years
Stock Options | Minimum
Stock Option Program
Vesting period	1 year