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Retirement Plans and Other Postretirement Benefits - Narrative (Details) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2020 USD ($) plan | Dec. 31, 2019 USD ($) | Dec. 31, 2018 USD ($) | Dec. 31, 2006 USD ($)
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Number of supplemental defined benefit plans frozen | plan | 2 |  |  |
Pension cost (credit) | $ 10.0 | $ 9.3 | $ 8.9 |
Health reimbursement account, amount | 1.3 |  |  | $ 7.3
Health reimbursement accounts funding | $ 0.1 | $ 0.1 | $ 0.1 |
Equity securities |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined benefit pension plan to approximate allocation | 35.00% |  |  |
Fixed income funds |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined benefit pension plan to approximate allocation | 65.00% |  |  |
Defined Benefit Plan |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Expected amortization of gain (loss) next year | $ 0.5 |  |  |
Supplemental Defined Benefit Plans |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Expected amortization of gain (loss) next year | $ 0.4 |  |  |
Qualified Plan |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Number of retirement plans | plan | 2 |  |  |
Qualified Plan | 401(k) plan | Defined Benefit Plan |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Frozen supplemental defined benefit plans, vesting percentage | 100.00% |  |  |
Employer matching contribution as percent of employees' gross pay | 3.00% |  |  |
Percentage of employer match | 5.00% |  |  |
Vesting period for Company contributions | 5 years |  |  |
Nonqualified Plan |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Number of retirement plans | plan | 3 |  |  |

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- Definition Frozen Supplemental Defined Benefit Plans, Vesting Percentage + References No definition available. + Details
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- Definition Health reimbursement account balance. + References No definition available. + Details
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- Definition Number Of Supplemental Defined Benefit Plans Frozen + References No definition available. + 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 Amount included in accumulated other comprehensive income (loss) for gain (loss) of defined benefit plan expected to be recognized in net periodic benefit (cost) credit for fiscal year following most recent annual statement of financial position. + References Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (s) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 + Details
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