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Summary of Significant Accounting Policies - Composition of Underlying Assets Comprising Company's Deferred Compensation Plans Assets (Details) - USD ($) $ in Thousands | Sep. 30, 2021 | Dec. 31, 2020
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Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items] |  |
Employee deferred compensation trust assets | $ 462,260 | $ 406,634
Quoted Prices in Active Markets for Identical Assets (Level 1) |  |
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items] |  |
Employee deferred compensation trust assets | 462,260 | 406,634
Significant Other Observable Inputs (Level 2) |  |
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items] |  |
Employee deferred compensation trust assets | 0 | 0
Significant Unobservable Inputs (Level 3) |  |
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items] |  |
Employee deferred compensation trust assets | 0 | 0
Money market funds |  |
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items] |  |
Employee deferred compensation trust assets | 65,681 | 69,681
Money market funds | Quoted Prices in Active Markets for Identical Assets (Level 1) |  |
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items] |  |
Employee deferred compensation trust assets | 65,681 | 69,681
Money market funds | Significant Other Observable Inputs (Level 2) |  |
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items] |  |
Employee deferred compensation trust assets | 0 | 0
Money market funds | Significant Unobservable Inputs (Level 3) |  |
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items] |  |
Employee deferred compensation trust assets | 0 | 0
Mutual funds - bond |  |
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items] |  |
Employee deferred compensation trust assets | 29,720 | 27,282
Mutual funds - bond | Quoted Prices in Active Markets for Identical Assets (Level 1) |  |
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items] |  |
Employee deferred compensation trust assets | 29,720 | 27,282
Mutual funds - bond | Significant Other Observable Inputs (Level 2) |  |
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items] |  |
Employee deferred compensation trust assets | 0 | 0
Mutual funds - bond | Significant Unobservable Inputs (Level 3) |  |
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items] |  |
Employee deferred compensation trust assets | 0 | 0
Mutual funds - stock |  |
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items] |  |
Employee deferred compensation trust assets | 278,816 | 234,667
Mutual funds - stock | Quoted Prices in Active Markets for Identical Assets (Level 1) |  |
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items] |  |
Employee deferred compensation trust assets | 278,816 | 234,667
Mutual funds - stock | Significant Other Observable Inputs (Level 2) |  |
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items] |  |
Employee deferred compensation trust assets | 0 | 0
Mutual funds - stock | Significant Unobservable Inputs (Level 3) |  |
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items] |  |
Employee deferred compensation trust assets | 0 | 0
Mutual funds - blend |  |
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items] |  |
Employee deferred compensation trust assets | 88,043 | 75,004
Mutual funds - blend | Quoted Prices in Active Markets for Identical Assets (Level 1) |  |
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items] |  |
Employee deferred compensation trust assets | 88,043 | 75,004
Mutual funds - blend | Significant Other Observable Inputs (Level 2) |  |
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items] |  |
Employee deferred compensation trust assets | 0 | 0
Mutual funds - blend | Significant Unobservable Inputs (Level 3) |  |
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items] |  |
Employee deferred compensation trust assets | $ 0 | $ 0

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