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Employee Incentive Plans - Summary of Weighted-Average Grant-Date Fair Value per Share for Shares Granted by Type of Award (Details) - $ / shares | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Restricted Stock And Restricted Stock Units |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |
Grant date fair value | $ 71.75 | $ 97.52 | $ 96.40
Performance Shares |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |
Grant date fair value | $ 99.87 | $ 124.10 | $ 109.38

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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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