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Stock-Based Compensation Plans (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions |  | 12 Months Ended
--- | --- | ---
Mar. 26, 2012 | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Shares available for issuance |  | 121,621 |  |
Fair value of shares vested |  | $ 7.9 | $ 4.8 | $ 5.6
Intrinsic value of restricted stock units exercised |  | $ 36.9 | $ 0.5 | $ 6.9
Weighted average recognition period |  | 1 year 8 months 12 days |  |
Restricted Stock [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Weighted average fair value of shares granted |  | $ 441.54 | $ 317.87 | $ 200.79
Restricted Stock Units (RSUs) [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Weighted average fair value of shares granted |  | $ 453.64 | $ 363.11 | $ 206.45
Restricted stock units converted to common stock, shares |  | 87,842 |  |
Ten Year Vesting [Member] | Restricted Stock Units (RSUs) [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Vesting period |  | 10 years |  |
Five Year Vesting [Member] | Restricted Stock Units (RSUs) [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Vesting period |  | 5 years |  |
Three Year Vesting [Member] | Restricted Stock Units (RSUs) [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Vesting period |  | 4 years |  |
Minimum [Member] | Fifteen Year Vesting [Member] | Restricted Stock [Member] | Chief Executive Officer [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Vesting period |  | 15 years |  |
Minimum [Member] | Three Year Vesting [Member] | Restricted Stock [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Vesting period |  | 3 years |  |
Incentive Plan [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Number of additional shares authorized for issuance | 500,000 |  |  |
Total authorized shares for plan issuance |  | 2,000,000.0 |  |

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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=116856206&loc=d3e5070-113901 + Details
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