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Investments - Additional Information (Detail) - USD ($) | 12 Months Ended |
--- | --- | ---
Dec. 26, 2020 | Dec. 28, 2019
Debt Securities, Available-for-sale [Line Items] |  |
Investments maximum maturity period | 5 years |
Unrealized gain (loss), net of unrealized gains/losses, on the investments in the bond portfolio | $ 3,578,000 | $ 1,427,000
Guarantee Payment of Insurance Claims |  |
Debt Securities, Available-for-sale [Line Items] |  |
Letters of credit outstanding | 64,934,000 |
Current Investments |  |
Debt Securities, Available-for-sale [Line Items] |  |
Investments providing collateral for letters of credit to guarantee insurance claims | 41,375,000 |
Non-Current Investments |  |
Debt Securities, Available-for-sale [Line Items] |  |
Investments providing collateral for letters of credit to guarantee insurance claims | 30,774,000 |
Total non-current investments | $ 81,216,000 |

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