Capital Stock (Tables)

12 Months Ended

Dec. 31, 2017

Capital Stock [Abstract]

Schedule of Fair Value Assumptions

Option Value and Assumptions
	2017			2016			2015
Weighted-average fair value per share	$	22.43		$	17.73		$	22.55
Assumptions:
Risk-free interest rate	2.0		%	1.3		%	1.8		%
Expected dividend yield	1.5		%	1.6		%	1.6		%
Expected stock price volatility	19.4		%	20.5		%	25.5		%
Expected option life (years)	6.0			6.1			7.3

Summary of Stock Option Activity

2017 Stock Option Activity
	Shares (in millions)		Weighted Average Exercise Price		Weighted-Average Remaining Term (in years)	Aggregate Intrinsic Value
Outstanding January 1	14.9		$	73.14
Granted	2.9		122.66
Exercised	(2.5	)	62.66
Canceled	(0.6	)	97.87
Outstanding December 31	14.7		$	83.71	5.4	$	956.5
Exercisable December 31	7.5		$	65.47	4.2	$	666.8
Options expected to vest	6.6		$	101.83	7.9	$	347.9

Summary of RSU and PSU Activity

Restricted Stock Units (RSUs) and Performance Stock Units (PSUs) Activity
	Shares (in millions)				Weighted Average Grant Date Fair Value
	RSUs		PSUs		RSUs		PSUs
Nonvested on January 1	1.1		0.3		$	90.10	$	91.19
Granted	0.5		0.1		117.44		122.41
Vested	(0.5	)	(0.1	)	87.08		81.14
Canceled or forfeited	(0.1	)	—		102.01		92.18
Nonvested on December 31	1.0		0.3		$	104.85	$	104.51