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Benefit Plans - Pension Assets by Fair Value Level (Details) - USD ($) $ in Thousands	Dec. 28, 2019	Dec. 29, 2018
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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Percentage of mutual funds owned that are actively managed funds.

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Percentage of mutual funds owned that are indexed funds.

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Percent of mutual funds' assets that are invested in non-U.S. equities.

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Percent of mutual funds' assets that are invested in non-U.S. fixed income securities.

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Percent of mutual funds' assets that are invested in U.S. fixed income securities.

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Amount of asset segregated and restricted to provide benefit under defined benefit plan. Asset includes, but is not limited to, stock, bond, other investment, earning from investment, and contribution by employer and employee.

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