EMPLOYEE BENEFITS - Investment assets (Details) - Pension plan - USD ($) $ in Thousands	12 Months Ended
Dec. 29, 2019	Dec. 30, 2018
Changes in the fair value of the plan's Level 3 investment assets
Fair value of plan assets, beginning of year	$ 1,259,979	$ 1,477,926
Fair value of plan assets, end of year	1,393,267	1,259,979
Level 3
Changes in the fair value of the plan's Level 3 investment assets
Fair value of plan assets, beginning of year	65,007	67,559
Realized gains (losses), net	2,741	4,531
Transfer in or out of level 3	(4,953)	(8,601)
Unrealized gains (losses), net	3,866	1,518
Fair value of plan assets, end of year	66,661	65,007
Real Estate
Changes in the fair value of the plan's Level 3 investment assets
Fair value of plan assets, beginning of year	55,398
Fair value of plan assets, end of year	55,874	55,398
Real Estate \| Level 3
Changes in the fair value of the plan's Level 3 investment assets
Fair value of plan assets, beginning of year	55,398	58,050
Realized gains (losses), net	2,738	4,528
Transfer in or out of level 3	(4,953)	(8,601)
Unrealized gains (losses), net	2,691	1,421
Fair value of plan assets, end of year	55,874	55,398
Private Equity
Changes in the fair value of the plan's Level 3 investment assets
Fair value of plan assets, beginning of year	9,609
Fair value of plan assets, end of year	10,787	9,609
Private Equity \| Level 3
Changes in the fair value of the plan's Level 3 investment assets
Fair value of plan assets, beginning of year	9,609	9,509
Realized gains (losses), net	3	3
Unrealized gains (losses), net	1,175	97
Fair value of plan assets, end of year	$ 10,787	$ 9,609

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

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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.

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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

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- Definition

Amount, measured using unobservable inputs, of increase (decrease) in plan assets of defined benefit plan, for assets transferred into (out of) Level 3 of fair value hierarchy. Includes, but is not limited to, transfer due to change in observability of significant inputs.

+ References

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