Stock-Based Compensation - Stock Options (Details) - Stock Options - USD ($) $ / shares in Units, $ in Millions	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Stock Option Program
Balance at the beginning of the period	36,196,232
Granted - Annual	5,409,628
Exercised	(4,667,165)
Canceled	(122,880)
Balance at the end of the period	36,815,815
Options exercisable	26,069,052
Options exercisable, exercise price	$ 107.43
Weighted average exercise price - Beginning balance	112.07
Weighted average exercise price - Granted - Annual	175.93
Weighted average exercise price - Exercised	89.38
Weighted average exercise price - Canceled	161.12
Weighted average exercise price - Ending balance	$ 124.16
Weighted average remaining contractual life for options outstanding	75 months
Weighted average remaining contractual life for options exercisable	61 months
Aggregate intrinsic value for options outstanding	$ 3,093
Aggregate intrinsic value for options exercisable	$ 2,627
Expiration of annual grants	10 years
Compensation expense yet to be recognized	$ 104
Expense recognition period	23 months
Total intrinsic value of stock options exercised	$ 465	$ 469
Cash received from options exercised	416	534
Tax benefit realized from exercise of stock options	$ 158	$ 173
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