Stock Option Plans (Tables)

9 Months Ended

Sep. 30, 2018

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Black-Scholes Option Pricing Model with Weighted Average

For purposes of expense recognition, the estimated fair values of the stock option grants are amortized to expense over the options’ vesting period. We estimated the fair value of stock options at the date of grant using the Black-Scholes option pricing model with the following weighted average assumptions:

	2018			2017
Expected dividend yield		2.3	%		2.8	%
Expected risk-free interest rate		2.7	%		2.3	%
Volatility		15.1	%		27.2	%
Expected life (in years)		5.5			5.0

Stock Option Activity and Related Information

The following is a summary of our stock option activity and related information for 2018 (in millions, except exercise price and year data):

	Nine-month period ended September 30, 2018
						Weighted
						Average
				Weighted		Remaining
	Shares			Average		Contractual		Aggregate
	Under			Exercise		Term		Intrinsic
	Option			Price		(in years)		Value
Beginning balance		9.5		$	45.27
Granted		1.3			70.74
Exercised		(1.4	)		37.55
Forfeited or canceled		(0.3	)		49.10
Ending balance		9.1		$	49.93		4.05	$	221.8
Exercisable at end of period		2.3		$	42.59		2.02	$	72.7
Ending vested and expected to vest		6.6		$	52.10		4.70	$	146.5

Other Information Regarding Stock Options Outstanding and Exercisable

Other information regarding stock options outstanding and exercisable at September 30, 2018 is summarized as follows (in millions, except exercise price and year data):

					Options Outstanding						Options Exercisable
Range of Exercise Prices					Number Outstanding		Weighted Average Remaining Contractual Term (in years)		Weighted Average Exercise Price		Number Exercisable		Weighted Average Exercise Price
$	35.71	-	$	39.17		1.1		1.14	$	38.08		1.1	$	38.08
	43.71	-		43.71		2.3		4.46		43.71		—		—
	46.17	-		46.87		2.9		3.00		46.49		1.2		46.61
	47.92	-		63.60		1.6		5.45		56.81		—		—
	70.74	-		70.74		1.2		6.46		70.74		—		—
$	35.71	-	$	70.74		9.1		4.05	$	49.93		2.3	$	42.59