Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2016

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Assumptions Used Relating to Valuation of Stock Options

The following table summarizes the assumptions used related to the valuation of our stock options during 2016, 2015, and 2014:



	Grant Year
	2016	2015	2014
Risk-free interest rate	1.16% - 1.55%	0.76% - 1.86%	1.11% - 2.04%
Expected dividend yield	—	—	—
Expected term	4 - 7 years	2 - 7 years	4 - 7 years
Expected volatility	29% - 31%	24% - 34%	25% - 36%

Stock Option Activity

The following table summarizes stock option activity during 2016:



	Stock Options
	Shares (in millions)			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (Years)	Aggregate Intrinsic Value (in millions)
Options outstanding at January 1	4.6			$	45.07
Granted ⁽¹⁾	0.9			$	52.53
Exercised	(0.3	)		$	31.21
Forfeited	—			$	—
Expired	—			$	—
Options outstanding as of December 31	5.2			$	46.99	6.54	$	31.8
Options exercisable at December 31	2.9			$	40.33	5.27	$	31.4
Options exercisable at December 31 and expected to vest thereafter	5.2			$	46.92	6.53	$	31.8
Options available for future grants at December 31	3.3		⁽²⁾


⁽¹⁾	The options granted during 2016 are related to our annual employee stock option award grant on March 1, 2016

⁽²⁾

Includes 2.5 million shares available under the 2008 Plan and 0.9 million shares available under the 2014 Director Plan. As noted above, the number of shares available under the 2014 Director Plan was reduced by 0.4 million shares in January 2017. If our stockholders approve the 2017 Plan, under which 5.5 million shares would be available for issuance, then no additional awards will be granted under the 2008 Plan, and the 2.5 million shares available under the 2008 Plan will no longer be available for issuance.

Weighted Average Grant-Date Fair Value of Stock Options Granted and Total Intrinsic Value of Stock Options Exercised

The weighted average grant-date fair value of stock options granted and total intrinsic value of stock options exercised are summarized in the following table:



	2016		2015		2014
Weighted average grant-date fair value of stock options granted	$	17.96	$	19.38	$	20.56
Total intrinsic value of stock options exercised (in millions)	$	5.3	$	51.9	$	56.2

Restricted Stock Activity

The following table summarizes information about vested and unvested restricted stock for 2016:



	Restricted Stock
	Shares (in actual number of shares)		Weighted-Average Grant Date Fair Value
Nonvested at January 1	284,284		$	53.11
Granted ⁽¹⁾	143,424		$	52.23
Vested	(128,640	)	$	49.26
Forfeited	(32,162	)	$	55.23
Nonvested at December 31	266,906		$	54.23


⁽¹⁾	The restricted stock awards granted during 2016 are primarily related to our employee annual restricted stock award grant in March 2016.

Weighted Average Grant-Date Fair Value of Restricted Stock Awards Granted and Total Fair Value of Restricted Stock Awards Vested

The weighted average grant-date fair value of restricted stock awards granted and total fair value of restricted stock awards vested are summarized in the following table:



	2016		2015		2014
Weighted average grant-date fair value of restricted stock awards granted	$	52.23	$	62.54	$	52.87
Total fair value of restricted stock awards vested (in millions)	$	6.4	$	8.8	$	8.1

Weighted Average Grant-Date Fair Value of Restricted Stock Units Granted and Total Fair Value of Restricted Stock Units Granted and Vested

The weighted average grant-date fair value and total grant-date fair value of RSUs granted (and vested) are summarized in the following table:



	2016		2015		2014
Weighted average grant-date fair value of RSUs granted	$	58.69	$	60.04	$	53.57
Total fair value of RSUs granted (in millions)	$	2.3	$	2.7	$	2.1

Total Stock-Based Compensation Expense

The following table summarizes the total stock-based compensation expense recognized in Selling, General, and Administrative Expenses in the Consolidated Statements of Income and the total recognized tax benefit related thereto:



	2016		2015		2014
Stock options	$	16.2	$	14.8	$	18.4
Restricted stock	6.6		6.5		5.8
RSUs	2.3		2.7		2.1
Total stock-based compensation expense	$	25.1	$	24.0	$	26.3

Tax benefit related to stock-based compensation expense	$	9.6	$	9.2	$	10.0