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Benefit Plans - Pension Assets by Fair Value Level (Details) - USD ($) $ in Thousands | Dec. 30, 2017 | Dec. 31, 2016
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Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Plan assets | $ 186,336 | $ 169,140
Approximate percentage of common stock invested in major industry | 91.00% | 90.00%
Approximate percentage of mutual funds actively managed | 66.00% | 68.00%
Approximate percentage of mutual funds indexed funds | 34.00% | 32.00%
Percentage of mutual funds' assets invested in U.S equities | 5.00% | 5.00%
Percent of mutual funds assets invested in non US equities | 41.00% | 38.00%
Percent of mutual funds assets invested in US fixed income securities | 52.00% | 54.00%
Percent of mutual funds assets invested in non US fixed income securities | 2.00% | 3.00%
Level 1 [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Plan assets | $ 24,889 | $ 28,418
Level 2 [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Plan assets | 156,442 | 136,027
Level 3 [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Plan assets | 5,005 | 4,695
Cash and Cash Equivalents [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Plan assets | 5,364 | 4,245
Cash and Cash Equivalents [Member] | Level 1 [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Plan assets | 5,364 | 4,245
Cash and Cash Equivalents [Member] | Level 2 [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Plan assets | 0 | 0
Cash and Cash Equivalents [Member] | Level 3 [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Plan assets | 0 | 0
Common Stock [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Plan assets | 11,113 | 18,601
Common Stock [Member] | Level 1 [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Plan assets | 11,113 | 18,601
Common Stock [Member] | Level 2 [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Plan assets | 0 | 0
Common Stock [Member] | Level 3 [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Plan assets | 0 | 0
Mutual Funds [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Plan assets | 164,854 | 141,599
Mutual Funds [Member] | Level 1 [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Plan assets | 8,412 | 5,572
Mutual Funds [Member] | Level 2 [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Plan assets | 156,442 | 136,027
Mutual Funds [Member] | Level 3 [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Plan assets | 0 | 0
Limited Partnerships [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Plan assets | 5,005 | 4,695
Limited Partnerships [Member] | Level 1 [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Plan assets | 0 | 0
Limited Partnerships [Member] | Level 2 [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Plan assets | 0 | 0
Limited Partnerships [Member] | Level 3 [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Plan assets | $ 5,005 | $ 4,695

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- Definition This represents the entire assets recognized in the balance sheet that are associated with the defined benefit plans. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.10) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.10) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=64852052&loc=d3e1703-114919 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 + Details
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