Stock-Based Compensation - Stock Options (Details) - Stock Options - USD ($) $ / shares in Units, $ in Millions	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Stock Option Program
Balance at the beginning of the period	38,552,445
Granted - Annual	5,591,727
Exercised	(6,201,880)
Canceled	(136,887)
Balance at the end of the period	37,805,405
Options exercisable	26,739,297
Options exercisable, exercise price	$ 95.14
Weighted average exercise price - Beginning balance	102.01
Weighted average exercise price - Granted - Annual	147.99
Weighted average exercise price - Exercised	86.81
Weighted average exercise price - Canceled	147.97
Weighted average exercise price - Ending balance	$ 111.14
Weighted average remaining contractual life for options outstanding	74 months
Weighted average remaining contractual life for options exercisable	61 months
Aggregate intrinsic value for options outstanding	$ 2,419
Aggregate intrinsic value for options exercisable	$ 2,139
Expiration of annual grants	10 years
Compensation expense yet to be recognized	$ 105
Expense recognition period	24 months
Total intrinsic value of stock options exercised	$ 469	$ 366
Cash received from options exercised	534	376
Tax benefit realized from exercise of stock options	$ 173	$ 136
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	$ 147.87
Risk-free interest rate (as a percent)	1.50%
Dividend yield (as a percent)	2.50%
Expected volatility (as a percent)	20.80%
Expected life	77 months
Black-Scholes fair value	$ 22.47