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Stock-Based Compensation (Tables) | 12 Months Ended
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Dec. 31, 2015
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 2015, 2014, and 2013:
| Grant Year
| 2015 |  | 2014 |  | 2013
Risk-free interest rate | 0.76% - 1.86% |  |  | 1.11% - 2.04% |  |  | 0.58% - 2.24% |
Expected dividend yield | — |  |  | — |  |  | — |
Expected term | 2 - 7 years |  |  | 4 - 7 years |  |  | 4 - 7 years |
Expected volatility | 24% - 34% |  |  | 25% - 36% |  |  | 29% - 44% |
Stock Option Activity | The following table summarizes stock option activity during 2015:
| 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 | 5.0 |  |  | $ | 36.43 |  |  |  |  |
Granted (1) | 1.0 |  |  | $ | 62.06 |  |  |  |  |
Exercised | (1.3 | ) |  | $ | 23.33 |  |  |  |  |
Forfeited | (0.1 | ) |  | $ | 51.50 |  |  |  |  |
Expired | — |  |  | $ | — |  |  |  |  |
Options outstanding as of December 31 | 4.6 |  |  | $ | 45.07 |  |  | 6.89 |  | $ | 70.1 |
Options exercisable at December 31 | 2.3 |  |  | $ | 35.09 |  |  | 5.55 |  | $ | 57.1 |
Options exercisable at December 31 and expected to vest thereafter | 4.6 |  |  | $ | 44.76 |  |  | 6.80 |  | $ | 70.4 |
Options available for future grants at December 31 | 4.3 |  |  |  |  |  |  |
(1) | The options granted during 2015, are primarily related to our employee quarterly stock option award grants in March, June, September, and December 2015.
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:
| 2015 |  | 2014 |  | 2013
Weighted average grant-date fair value of stock options granted | $ | 19.38 |  |  | $ | 20.56 |  |  | $ | 17.93 |
Total intrinsic value of stock options exercised (in millions) | $ | 51.9 |  |  | $ | 56.2 |  |  | $ | 31.3 |
Restricted Stock Activity | The following table summarizes information about vested and unvested restricted stock for 2015:
| Restricted Stock
| Shares (in actual number of shares) |  | Weighted-Average Grant Date Fair Value
Nonvested at January 1 | 306,442 |  |  | $ | 42.52 |
Granted (1) | 159,442 |  |  | $ | 62.54 |
Vested | (140,019 | ) |  | $ | 41.44 |
Forfeited | (41,581 | ) |  | $ | 48.02 |
Nonvested at December 31 | 284,284 |  |  | $ | 53.11 |
(1) | The restricted stock awards granted during 2015 are primarily related to our employee annual restricted stock award grant in March 2015.
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:
| 2015 |  | 2014 |  | 2013
Weighted average grant-date fair value of restricted stock awards granted | $ | 62.54 |  |  | $ | 52.87 |  |  | $ | 43.45 |
Total fair value of restricted stock awards vested (in millions) | $ | 8.8 |  |  | $ | 8.1 |  |  | $ | 6.8 |
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:
| 2015 |  | 2014 |  | 2013
Weighted average grant-date fair value of RSUs granted | $ | 60.04 |  |  | $ | 53.57 |  |  | $ | — |
Total fair value of RSUs granted (in millions) | $ | 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:
| 2015 |  | 2014 |  | 2013
Stock options | $ | 14.8 |  |  | $ | 18.4 |  |  | $ | 16.6 |
Restricted stock | 6.5 |  |  | 5.8 |  |  | 4.7 |
RSUs | 2.7 |  |  | 2.1 |  |  | — |
Total stock-based compensation expense | $ | 24.0 |  |  | $ | 26.3 |  |  | $ | 21.3 |
Tax benefit related to stock-based compensation expense | $ | 9.2 |  |  | $ | 10.0 |  |  | $ | 8.1 |

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- Definition Tabular disclosure of the number and weighted-average exercise prices (or conversion ratios) for share options (or share units) that were outstanding at the beginning and end of the year, vested and expected to vest, exercisable or convertible at the end of the year, and the number of share options or share units that were granted, exercised or converted, forfeited, and expired during the year. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Tabular disclosure of the significant assumptions used during the year to estimate the fair value of stock options, including, but not limited to: (a) expected term of share options and similar instruments, (b) expected volatility of the entity's shares, (c) expected dividends, (d) risk-free rate(s), and (e) discount for post-vesting restrictions. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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