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Benefit Plans - Pension Assets by Fair Value Level (Details) - USD ($) $ in Thousands | Dec. 28, 2019 | Dec. 29, 2018
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Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Long-term asset | $ 183,486 | $ 164,603
Approximate percentage of mutual funds actively managed | 80.00% | 61.00%
Approximate percentage of mutual funds indexed funds | 20.00% | 39.00%
Percentage of mutual funds' assets invested in U.S equities | 10.00% | 5.00%
Percent of mutual funds assets invested in non US equities | 28.00% | 35.00%
Percent of mutual funds assets invested in US fixed income securities | 62.00% | 59.00%
Percent of mutual funds assets invested in non US fixed income securities |  | 1.00%
Level 1 [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Long-term asset | $ 12,318 | $ 12,984
Level 2 [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Long-term asset | 163,253 | 146,591
Level 3 [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Long-term asset | 7,915 | 5,028
Cash and Cash Equivalents [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Long-term asset | 12,318 | 12,984
Cash and Cash Equivalents [Member] | Level 1 [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Long-term asset | 12,318 | 12,984
Cash and Cash Equivalents [Member] | Level 2 [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Long-term asset | 0 | 0
Cash and Cash Equivalents [Member] | Level 3 [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Long-term asset | 0 | 0
Mutual Funds [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Long-term asset | 163,253 | 146,591
Mutual Funds [Member] | Level 1 [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Long-term asset | 0 | 0
Mutual Funds [Member] | Level 2 [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Long-term asset | 163,253 | 146,591
Mutual Funds [Member] | Level 3 [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Long-term asset | 0 | 0
Limited Partnerships [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Long-term asset | 7,915 | 5,028
Limited Partnerships [Member] | Level 1 [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Long-term asset | 0 | 0
Limited Partnerships [Member] | Level 2 [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Long-term asset | 0 | 0
Limited Partnerships [Member] | Level 3 [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Long-term asset | $ 7,915 | $ 5,028

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