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Stock-Based Compensation (Tables) | 12 Months Ended
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Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract] |
Restricted Stock Unit Activity | The following table summarizes information about vested and unvested RSUs for 2017:
| RSUs
| Shares (in actual number of shares) |  | Weighted-Average Grant Date Fair Value
Nonvested at January 1 | — |  |  | $ | — |
Granted (1) | 632,255 |  |  | $ | 43.66 |
Vested | (45,657 | ) |  | $ | 49.28 |
Forfeited | (66,989 | ) |  | $ | 43.30 |
Nonvested at December 31 | 519,609 |  |  | $ | 43.22 |
(1) | The RSUs granted during 2017 are primarily related to our employee annual equity award grant in April 2017 and non-employee director annual equity award grant in January 2017.
Weighted Average Grant-Date Fair Value of Restricted Stock Units Granted and Total Fair Value of Restricted Stock Units Vested | The weighted average grant-date fair value of RSUs and total fair value of RSUs vested are summarized in the following table:
| 2017 |  | 2016 |  | 2015
Weighted average grant-date fair value of RSUs granted | $ | 43.66 |  |  | $ | 58.69 |  |  | $ | 60.04 |
Total fair value of RSUs vested (in millions) | $ | 2.2 |  |  | $ | 2.3 |  |  | $ | 2.7 |
Assumptions Used Related to Valuation of Stock Options | The following table summarizes the assumptions used related to the valuation of our stock options granted during 2016 and 2015:
| 2016 |  | 2015
Risk-free interest rate | 1.16% - 1.55% |  |  | 0.76% - 1.86% |
Expected dividend yield | — |  |  | — |
Expected term | 4 - 7 years |  |  | 2 - 7 years |
Expected volatility | 29% - 31% |  |  | 24% - 34% |
Stock Option Activity | The following table summarizes stock option activity during 2017:
| 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 | 5.2 |  |  | $ | 46.99 |  |  |  |  |
Granted | — |  |  | $ | — |  |  |  |  |
Exercised | (1.0 | ) |  | $ | 37.85 |  |  |  |  |
Forfeited | (0.2 | ) |  | $ | 56.35 |  |  |  |  |
Expired | (0.3 | ) |  | $ | 54.91 |  |  |  |  |
Options outstanding as of December 31 | 3.7 |  |  | $ | 48.49 |  |  | 5.82 |  | $ | 23.4 |
Options exercisable at December 31 | 2.7 |  |  | $ | 45.65 |  |  | 5.19 |  | $ | 23.5 |
Options exercisable at December 31 and expected to vest thereafter | 3.7 |  |  | $ | 48.52 |  |  | 5.76 |  | $ | 23.5 |
Options available for future grants at December 31 | 5.4 |  |  |  |  |  |  |
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:
| 2017 |  | 2016 |  | 2015
Weighted average grant-date fair value of stock options granted | $ | — |  |  | $ | 17.96 |  |  | $ | 19.38 |
Total intrinsic value of stock options exercised (in millions) | $ | 11.9 |  |  | $ | 5.3 |  |  | $ | 51.9 |
Restricted Stock Activity | The following table summarizes information about vested and unvested restricted stock for 2017:
| Restricted Stock
| Shares (in actual number of shares) |  | Weighted-Average Grant Date Fair Value
Nonvested at January 1 | 266,906 |  |  | $ | 54.23 |
Granted | — |  |  | $ | — |
Vested | (100,341 | ) |  | $ | 51.99 |
Forfeited | (18,634 | ) |  | $ | 55.10 |
Nonvested at December 31 | 147,931 |  |  | $ | 55.65 |
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:
| 2017 |  | 2016 |  | 2015
Weighted average grant-date fair value of restricted stock awards granted | $ | — |  |  | $ | 52.23 |  |  | $ | 62.54 |
Total fair value of restricted stock awards vested (in millions) | $ | 4.2 |  |  | $ | 6.4 |  |  | $ | 8.8 |
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:
| 2017 |  | 2016 |  | 2015
RSUs | $ | 14.2 |  |  | $ | 2.3 |  |  | $ | 2.7 |
Stock options | 3.1 |  |  | 16.2 |  |  | 14.8 |
Restricted stock | 3.3 |  |  | 6.6 |  |  | 6.5 |
Total stock-based compensation expense | $ | 20.6 |  |  | $ | 25.1 |  |  | $ | 24.0 |
Tax benefit related to stock-based compensation expense | $ | 7.8 |  |  | $ | 9.6 |  |  | $ | 9.2 |

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- Definition Tabular disclosure for stock option plans. Includes, but is not limited to, outstanding awards at beginning and end of year, grants, exercises, forfeitures, and weighted-average grant date fair value. + 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 (d) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 Reference 3: 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=96867065&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=96867065&loc=d3e5070-113901 + Details
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