Investments - Additional Information (Detail) - USD ($)	12 Months Ended
Dec. 28, 2019	Dec. 29, 2018
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	$ 1,427,000	$ (1,184,000)
Guarantee Payment of Insurance Claims
Debt Securities, Available-for-sale [Line Items]
Letters of credit outstanding	61,503,000
Current Investments
Debt Securities, Available-for-sale [Line Items]
Investments providing collateral for letters of credit to guarantee insurance claims		32,770,000
Cash equivalents providing collateral for letter of credit to guarantee insurance claims		$ 131,000
Non-Current Investments
Debt Securities, Available-for-sale [Line Items]
Investments providing collateral for letters of credit to guarantee insurance claims	35,421,000
Total non-current investments	$ 84,838,000

Investments maximum maturity period, years

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- Definition

Amount before tax of unrealized gain (loss) in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

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- Definition

Amount of restricted investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 1A
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- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

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No definition available.

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- Definition

The total amount of investments that are intended to be held for an extended period of time (longer than one operating cycle).

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-Publisher FASB
-Name Accounting Standards Codification
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Amount of cash and cash equivalents restricted as to withdrawal or usage. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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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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