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Employee and Retiree Benefit Plans - Narrative (Details) $ in Thousands | 12 Months Ended | 120 Months Ended
--- | --- | ---
Dec. 31, 2020 USD ($) | Dec. 31, 2019 USD ($) | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($) | Dec. 31, 2016 USD ($) | Dec. 31, 2018
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |  |  |
Future annual rate of increase in cost of health care for 2016 to measure postretirement benefit obligations |  | 6.50% |  |  |  |
Ultimate rate of health care cost in 2028 and thereafter |  | 4.50% |  |  |  |
Plan asset, maximum investment in any one issuer |  | 10.00% |  |  |  |
Equity securities minimum market capitalization |  | $ 100,000 |  |  |  |
Fixed income portfolio, maximum average maturity years |  | 11 years |  |  |  |
Weighted average expected return on plan asset |  |  | 5.51% |  |  |
Basis used to determine expected return on plan asset, average expected investment expenses |  |  | 0.60% |  |  |
Perentage return on plan assets over the last ten years |  |  |  |  |  | 7.56%
Number of investments in hedge funds and other alternative investments |  | 3 |  |  |  |
Defined benefit plan, percentage of employer's matching contribution |  | 6.00% |  |  |  |
Thrift plan expense |  |  | $ 8,400 | $ 5,200 | $ 7,800 |
Third investment |  |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |  |  |
Domestic plan, investment lock up period |  | 2 years |  |  |  |
Equity Securities |  |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |  |  |
Weighted average expected return on plan asset |  |  | 6.30% |  |  |
Defined Benefit Plan, Fixed Income Securities |  |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |  |  |
Weighted average expected return on plan asset |  |  | 3.95% |  |  |
Defined Benefit Plan, Equity Funds |  |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |  |  |
Domestic plan, investment notice period |  | 10 days |  |  |  |
Pension Benefits |  |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |  |  |
Contributions to benefit plans |  | $ 25,915 | $ 24,357 |  |  |
Weighted average expected return on plan asset |  |  | 5.05% | 5.37% |  |
Pension Benefits | United States |  |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |  |  |
Contributions to benefit plans |  | 25,700 |  |  |  |
Pension Benefits | Foreign Plans |  |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |  |  |
Contributions to benefit plans |  | 200 |  |  |  |
Other Postretirement Benefits |  |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |  |  |
Contributions to benefit plans |  | 2,333 | $ 3,044 |  |  |
Weighted average expected return on plan asset |  |  | 0.00% | 0.00% |  |
Other Postretirement Benefits | United States |  |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |  |  |
Contributions to benefit plans |  | $ 2,300 |  |  |  |
Subsequent Event | Pension Benefits | United States |  |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |  |  |
Contributions to benefit plans | $ 30,600 |  |  |  |  |
Subsequent Event | Pension Benefits | Foreign Plans |  |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |  |  |
Contributions to benefit plans | 600 |  |  |  |  |
Subsequent Event | Other Postretirement Benefits | United States |  |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |  |  |
Contributions to benefit plans | $ 5,200 |  |  |  |  |
Second Investment |  |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |  |  |
Domestic plan, investment notice period |  | 90 days |  |  |  |
Third investment |  |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |  |  |
Domestic plan, investment notice period |  | 95 days |  |  |  |

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