Stock-Based Compensation - Stock Options (Details) - Stock Options - USD ($) $ / shares in Units, $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Stock Option Program
Balance at the beginning of the period	36,196,232
Granted - Annual	5,409,628
Exercised	(5,203,405)
Canceled	(137,827)
Balance at the end of the period	36,264,628
Options exercisable	25,532,812
Options exercisable, exercise price	$ 107.67
Weighted average exercise price - Beginning balance	112.07
Weighted average exercise price - Granted - Annual	175.93
Weighted average exercise price - Exercised	90.05
Weighted average exercise price - Canceled	161.38
Weighted average exercise price - Ending balance	$ 124.57
Weighted average remaining contractual life for options outstanding	72 months
Weighted average remaining contractual life for options exercisable	59 months
Aggregate intrinsic value for options outstanding	$ 3,095
Aggregate intrinsic value for options exercisable	$ 2,610
Expiration of annual grants	10 years
Compensation expense yet to be recognized	$ 85
Expense recognition period	22 months
Total intrinsic value of stock options exercised	$ 526	$ 573
Cash received from options exercised	468	630
Tax benefit realized from exercise of stock options	$ 179	$ 212
Maximum
Stock Option Program
Vesting period	3 years
Minimum
Stock Option Program
Vesting period	1 year
Annual Stock Option Program
Share- based compensation assumptions
Weighted average exercise price	$ 175.76
Risk-free interest rate (as a percent)	2.10%
Dividend yield (as a percent)	2.50%
Expected volatility (as a percent)	17.30%
Expected life	78 months
Black-Scholes fair value	$ 23.51