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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.2)
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Percentage of target investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(5)(i)
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No definition available.

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Fair Value Measurements - Narrative (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 30, 2016
Equity
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment committee equity target allocation percentage of pension assets	70.00%
Fixed Income
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment committee equity target allocation percentage of pension assets	30.00%
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Amortized cost basis of investments	$ 91	$ 500