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Benefit Plans - Pension Assets by Fair Value Level (Details) - USD ($) $ in Thousands | Dec. 25, 2021 | Dec. 26, 2020
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Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Long-term asset | $ 79,478 | $ 78,480
Approximate percentage of mutual funds actively managed | 78.00% | 76.00%
Approximate percentage of mutual funds indexed funds | 22.00% | 24.00%
Percentage of mutual funds' assets invested in U.S equities | 27.00% | 27.00%
Percent of mutual funds assets invested in non US equities | 73.00% | 73.00%
Level 1 |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Long-term asset | $ 292 | $ 492
Level 2 |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Long-term asset | 71,465 | 71,084
Level 3 |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Long-term asset | 7,721 | 6,904
Cash and money market funds |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Long-term asset | 292 | 492
Cash and money market funds | Level 1 |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Long-term asset | 292 | 492
Cash and money market funds | Level 2 |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Long-term asset | 0 | 0
Cash and money market funds | Level 3 |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Long-term asset | 0 | 0
Mutual Funds |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Long-term asset | 71,465 | 71,084
Mutual Funds | Level 1 |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Long-term asset | 0 | 0
Mutual Funds | Level 2 |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Long-term asset | 71,465 | 71,084
Mutual Funds | Level 3 |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Long-term asset | 0 | 0
Limited partnerships |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Long-term asset | 7,721 | 6,904
Limited partnerships | Level 1 |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Long-term asset | 0 | 0
Limited partnerships | Level 2 |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Long-term asset | 0 | 0
Limited partnerships | Level 3 |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Long-term asset | $ 7,721 | $ 6,904

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