Capital Stock (Tables)

12 Months Ended

Dec. 31, 2017

Capital [Abstract]

Summary of Stock Option Activity

A summary of stock option activity for the year ended December 31, 2017 is as follows:

	Number of Shares		Weighted-Average Option Price per Share		Weighted-Average Remaining Contractual Life (Years)	Aggregate Intrinsic Value
Outstanding at January 1, 2017	5.6		$	102.80
Granted	1.1		167.57
Exercised	(2.2	)	89.88
Forfeited or expired	(0.2	)	142.51
Outstanding at December 31, 2017	4.3		124.31		6.15	$	433.0
Exercisable at December 31, 2017	2.6		107.07		4.72	$	312.3

Summary of Nonvested Restricted Stock Activity Including Restricted Stock Units

A summary of the status of nonvested restricted stock activity, including restricted stock units, for the year ended December 31, 2017 is as follows:

	Restricted Stock Shares and Units		Weighted-Average Grant Date Fair Value per Share
Nonvested at January 1, 2017	2.1		$	127.68
Granted	0.8		174.44
Vested	(0.8	)	110.39
Forfeited	(0.1	)	148.77
Nonvested at December 31, 2017	2.0		152.20

Summary of Weighted-Average Assumptions Used to Estimate the Fair Values of Options Granted During the Periods

The following weighted-average assumptions were used to estimate the fair values of options granted during the years ended December 31, 2017, 2016 and 2015:

	2017		2016		2015
Risk-free interest rate	2.31	%	1.76	%	1.96	%
Volatility factor	32.00	%	32.00	%	31.00	%
Dividend yield (annual)	1.60	%	2.00	%	1.70	%
Weighted-average expected life (years)	4.00		4.10		4.00

Schedule of Weighted-Average Fair Values Determined For the Periods

The following weighted-average fair values were determined for the years ending December 31, 2017, 2016 and 2015:

	2017		2016		2015
Options granted during the year	$	40.88	$	30.56	$	33.97
Restricted stock awards granted during the year	174.44		131.81		147.00

Summary of Cash Dividend Activity

A summary of the cash dividend activity for the years ended December 31, 2017 and 2016 is as follows:

Declaration Date	Record Date	Payment Date	Cash Dividend per Share		Total
Year ended December 31, 2017
February 22, 2017	March 10, 2017	March 24, 2017	$	0.65	$	172.2
April 27, 2017	June 9, 2017	June 23, 2017	0.65		171.8
July 25, 2017	September 8, 2017	September 25, 2017	0.70		181.4
October 24, 2017	December 5, 2017	December 21, 2017	0.70		179.5
Year ended December 31, 2016
February 18, 2016	March 10, 2016	March 25, 2016	$	0.65	$	170.7
April 26, 2016	June 10, 2016	June 24, 2016	0.65		170.9
July 26, 2016	September 9, 2016	September 26, 2016	0.65		171.1
November 1, 2016	December 5, 2016	December 21, 2016	0.65		171.3

Summary of Share Repurchases

A summary of common stock repurchases for the period January 1, 2018 through February 9, 2018 (subsequent to December 31, 2017) and for the year ended December 31, 2017 is as follows:

	January 1, 2018 through February 9, 2018		Year Ended December 31, 2017
Shares repurchased	0.7		10.5
Average price per share	$	237.35	$	189.93
Aggregate cost	$	156.6	$	1,997.7
Authorization remaining at end of year	$	7,021.5	$	7,178.1