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Benefit Plans - Pension Assets by Fair Value Level (Details) - USD ($) $ in Thousands | Dec. 29, 2018 | Dec. 30, 2017
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Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Long-term asset | $ 164,603 | $ 186,336
Approximate percentage of mutual funds actively managed | 61.00% | 66.00%
Approximate percentage of mutual funds indexed funds | 39.00% | 34.00%
Percentage of mutual funds' assets invested in U.S equities | 5.00% | 5.00%
Percent of mutual funds assets invested in non US equities | 35.00% | 41.00%
Percent of mutual funds assets invested in US fixed income securities | 59.00% | 52.00%
Percent of mutual funds assets invested in non US fixed income securities | 1.00% | 2.00%
Approximate percentage of common stock invested in major industry |  | 91.00%
Level 1 [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Long-term asset | $ 12,984 | $ 24,889
Level 2 [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Long-term asset | 146,591 | 156,442
Level 3 [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Long-term asset | 5,028 | 5,005
Cash and Cash Equivalents [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Long-term asset | 12,984 | 5,364
Cash and Cash Equivalents [Member] | Level 1 [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Long-term asset | 12,984 | 5,364
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
Defined Benefit Plan, Equity Securities, Common Stock [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Long-term asset |  | 11,113
Defined Benefit Plan, Equity Securities, Common Stock [Member] | Level 1 [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Long-term asset |  | 11,113
Defined Benefit Plan, Equity Securities, Common Stock [Member] | Level 2 [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Long-term asset |  | 0
Defined Benefit Plan, Equity Securities, Common Stock [Member] | Level 3 [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Long-term asset |  | 0
Mutual Funds [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Long-term asset | 146,591 | 164,854
Mutual Funds [Member] | Level 1 [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Long-term asset | 0 | 8,412
Mutual Funds [Member] | Level 2 [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Long-term asset | 146,591 | 156,442
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 | 5,028 | 5,005
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 | $ 5,028 | $ 5,005

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