| **Pension and Other Postretirement Benefits - Additional Information (Details) - USD ($) $ in Thousands** | 3 Months Ended | 9 Months Ended |        |
|-----------------------------------------------------------------------------------------------------------|----------------|----------------|--------|
||
| **Weighted-average assumptions used to determine benefit obligation:**                                    |           |           |   |
| Weighted-average discount rate, rounded amount                                                            |           | 0.25%          |   |
| Cash contributions                                                                                        | $ 100          | $ 201          |   |
| Qualified Pension Plans [Member]                                                                          |           |           |   |
| **Weighted-average assumptions used to determine benefit obligation:**                                    |           |           |   |
| Effect of plan amendment on net periodic benefit cost                                                     | 445            | 445            |   |
| Effect of plan amendment on net periodic benefit cost compared to prior approach                          |           | 1,343          |   |
| Nonqualified Pension Plans [Member]                                                                       |           |           |   |
| **Weighted-average assumptions used to determine benefit obligation:**                                    |           |           |   |
| Effect of plan amendment on net periodic benefit cost                                                     | 58             | 58             |   |
| Effect of plan amendment on net periodic benefit cost compared to prior approach                          |           | 14             |   |
| Other Noncurrent Assets [Member]                                                                          |           |           |   |
| **Weighted-average assumptions used to determine benefit obligation:**                                    |           |           |   |
| Restricted trust, included in Other noncurrent assets                                                     | $ 641          | $ 641          | $ 729  |

| X                                                                                                                                                                                                                                                                                                                                                                                  |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
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+ References
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|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of contributions made by the employer to defined benefit plans.
+ References
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|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The amount of increase or decrease in net periodic benefit cost related to the effects of a change in the substantive terms of an existing defined benefit plan or the initiation of a new plan. A plan amendment may increase or decrease benefits, including those attributed to years of service already rendered.
+ References
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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.
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No definition available.
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| - Definition
Amount of investments in debt and equity securities and other forms of securities that provide ownership interests classified as trading.
+ References
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