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Stock-Based Compensation - Summary of Changes in SARs Outstanding (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2020
Weighted Average Remaining Contractual Term (Years) |  |  |
Granted | 2 years 4 months 24 days |  |
Stock appreciation rights |  |  |
SARs |  |  |
Outstanding, Beginning Balance (in shares) | 1.2 |  |
Granted (in shares) | 0.2 |  |
Forfeited (in shares) | (0.1) |  |
Exercised (in shares) | (0.3) |  |
Outstanding, Ending Balance (in shares) | 1.0 | 1.2 |
Vested and exercisable, ending balance (in shares) | 0.5 |  |
Per Share Weighted Average Exercise Price |  |  |
Outstanding, Beginning Balance (in dollars per share) | $ 104.05 |  |
Granted (in dollars per share) | 154.31 |  |
Forfeited (in dollars per share) | 110.85 |  |
Exercised (in dollars per share) | 78.63 |  |
Outstanding, Ending Balance (in dollars per share) | 123.59 | $ 104.05 |
Vested and exercisable, ending balance (in Dollars per share) |  |  | $ 104.97
Per Share Weighted Average Grant Date Fair Value |  |  |
Outstanding, Beginning Balance (in dollars per share) | 23.18 |  |
Granted (in dollars per share) | 34.92 |  |
Forfeited (in dollars per share) | 26.17 |  |
Exercised (in Dollars per share) | 16.89 |  |
Outstanding, Ending Balance (in dollars per share) | $ 27.76 | $ 23.18 |
Vested and exercisable, ending balance (in Dollars per share) |  |  | $ 23.30
Weighted Average Remaining Contractual Term (Years) |  |  |
Weighted average remaining contractual terms | 4 years 4 months 13 days | 4 years 2 months 15 days |
Granted | 6 years 1 month 6 days |  |
Weighted average remaining contractual terms vested and exercisable | 3 years 4 months 17 days |  |
Unvested SARs (in shares) | 1.0 | 1.2 | 1.0
Aggregate intrinsic value of outstanding shares |  |  | $ 38.4
Aggregate intrinsic value of shares vested and exercisable |  |  | $ 25.0
Stock appreciation rights | Unvested |  |  |
SARs |  |  |
Outstanding, Ending Balance (in shares) | 0.5 |  |
Weighted Average Remaining Contractual Term (Years) |  |  |
Unvested SARs (in shares) | 0.5 |  | 0.5

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- Definition The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(iv)(3) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(1) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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