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Stock-Based Compensation Plans - Stock-Based Awards (Details) - USD ($) shares in Millions, $ in Millions | 3 Months Ended | 195 Months Ended |
--- | --- | --- | ---
Mar. 31, 2021 | Mar. 31, 2020 | Mar. 31, 2021 | May 20, 2014
Stock-Based Compensation Plans |  |  |  |
Stock-Based Compensation Plans - Disclosures |  |  |  |
Compensation cost | $ 31.1 | $ 23.5 |  |
Related income tax benefit | 5.7 | 4.9 |  |
Capitalized as part of an asset | $ 0.5 | $ 0.4 |  |
Amended and Restated 2010 Stock Incentive Plan, 2005 Directors Stock Plan and 2014 Directors Stock Plan |  |  |  |
Stock-Based Compensation Plans - Disclosures |  |  |  |
Number of shares that will be granted |  |  |  | 0.0
Stock Incentive Plan and Directors Stock Plan |  |  |  |
Stock-Based Compensation Plans - Disclosures |  |  |  |
Options granted (in shares) |  |  | 0.0 |
Awards or units granted (in shares) |  |  | 0.0 |
2014 Stock Incentive Plan and 2020 Directors Stock Plan |  |  |  |
Stock-Based Compensation Plans - Disclosures |  |  |  |
Maximum number of new shares of common stock available for grant (in shares) | 2.3 |  | 2.3 |

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- Definition Represents the compensation cost capitalized during the period arising from share-based compensation arrangements (for example, shares of stock, stock options or other equity instruments) with employees and certain agents. + References No definition available. + Details
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- Definition Amount of tax benefit for recognition of expense of award under share-based payment arrangement. + 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 (h)(1)(i) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition The number of grants made 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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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Definition The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable. + 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 -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition Amount of cost expensed and capitalized for award under share-based payment arrangement. + 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 (h)(1) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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