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BENEFIT PLANS (Details) | 12 Months Ended
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Aug. 01, 2020 USD ($) agreement | Aug. 03, 2019 USD ($) employee agreement | Jul. 28, 2018 USD ($) | Jul. 29, 2017 USD ($)
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Number of union employees participating in multiemployer retirement plans under collective bargaining agreements |  | 50.00% |  |
Increase in accumulated postretirement benefit obligation |  | $ 700,000 |  |
Increase in service and interest cost |  | 100,000 |  |
Decrease in accumulated postretirement benefit obligation |  | 700,000 |  |
Decrease in service and interest cost |  | 100,000 |  |
Total employer contribution expenses |  | 21,000,000 | $ 11,600,000 | $ 10,100,000
Multiemployer plan, contributions by employer |  | $ 41,000,000 |  |
Number of employees | employee |  | 19,000 |  |
Employees covered by collective bargaining agreements | employee |  | 4,800 |  |
Number of collective bargaining agreements | agreement |  | 46 |  |
Number of initial collective bargaining agreements in progress | agreement |  | 2 |  |
Employees covered by initial collective bargaining agreements | employee |  | 33 |  |
Number of collective bargaining agreements renegotiated | agreement |  | 14 |  |
Employees covered by renegotiated collective bargaining agreements | employee |  | 1,300 |  |
Number of collective bargaining agreements expired | agreement |  | 6 |  |
Employees covered by expired collective bargaining agreements | employee |  | 550 |  |
Employees covered by collective bargaining agreements scheduled to expire | employee |  | 470 |  |
Minimum |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Contributions to defined benefit pension plans and postretirement benefit plans |  | $ 0 |  |
Maximum |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Contributions to defined benefit pension plans and postretirement benefit plans |  | $ 6,000,000 |  |
Retirement Plan, Before Age 65 | Postemployment Retirement Benefits |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Assumed healthcare cost trend rate (as a percent) |  | 7.30% |  |
Ultimate healthcare cost trend rate (as a percent) |  | 4.50% |  |
Retirement Plan, After Age 65 | Postemployment Retirement Benefits |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Assumed healthcare cost trend rate (as a percent) |  | 8.10% |  |
Ultimate healthcare cost trend rate (as a percent) |  | 4.50% |  |
Multiemployer Plans, Postretirement Benefit |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Multiemployer pension plan withdrawal liability |  | $ 3,400,000 |  |
Multiemployer plan, contributions by employer |  | 41,300,000 | $ 500,000 | $ 0
Multiemployer Plans, Health and Welfare Benefit | Multiemployer Plans, Postretirement Benefit |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Multiemployer plan, contributions by employer |  | 58,500,000 |  |
Unified Grocers, Inc. Cash Balance Plan |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Minimum pension contributions |  | 8,250,000 |  |
Subsequent Event |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Estimated actuarial loss | $ 0 |  |  |
Estimated amortization from accumulated other comprehensive gain into net periodic benefit cost | $ 3,100,000 |  |  |
Subsequent Event | Scenario, Forecast |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Number of collective bargaining agreements scheduled to expire | agreement | 6 |  |  |
SUPERVALU |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Multiemployer pension plan withdrawal liability |  | $ 35,700,000 |  |
Multiemployer pension plan, payment period |  | 20 years |  |

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