Retirement Plans - Reconciliation for fair value measurements that use significant unobservable inputs (Details) - Unobservable Inputs Level 3 - USD ($) $ in Millions	12 Months Ended
Dec. 29, 2018	Dec. 30, 2017
Reconciliation for fair value measurements that use significant unobservable inputs (Level 3)
Balance at beginning of year	$ 460
Balance at end of year	460	$ 460
Real estate
Reconciliation for fair value measurements that use significant unobservable inputs (Level 3)
Balance at beginning of year	460	494
Unrealized gains (losses), net	13	(6)
Realized gains, net	12	24
Purchases, sales and settlements, net	(25)	(52)
Balance at end of year	$ 460	$ 460

Amount, measured using unobservable inputs, of increase (decrease) in plan assets of defined benefit plan from actual return (loss) on assets sold.

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- Definition

Amount, measured using unobservable inputs, of increase (decrease) in plan assets of defined benefit plan from actual return (loss) on assets still held.

+ References

+ Details

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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+ Details

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- Definition

Amount, measured using unobservable input, of increase (decrease) in plan asset of defined benefit plan from purchase, sale and settlement of trade associated with underlying investment.

+ References

+ Details

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- Details

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- Details

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