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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Property and Equipment, Intangible Assets, Insurance, Fair Value Measurements and Accounting Pronouncements (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Sep. 30, 2019 | Sep. 30, 2018
Property and Equipment |  |
Impairment of property and equipment | $ 0.0 | $ 0.0
Goodwill and Intangible Assets: |  |
Intangible asset impairment charges | $ 2.9 |
Goodwill impairment charges |  | 1.9
Revenue Recognition |  |
Practical expedient, financing components | true |
Insurance |  |
Letter of credit issued for worker's compensation insurance carrier as part of the entity's self-insured loss control program | $ 0.5 |
Fair Value Measurements |  |
Intangible asset impairment charges | $ 2.9 |
Goodwill impairment charges |  | 1.9
Accounting Pronouncements |  |
Practical expedient, financing components | true |
Practical expedient to expense as incurred any incremental costs to obtain and fulfill customer contracts | true |
Retail Segment |  |
Goodwill and Intangible Assets: |  |
Intangible asset impairment charges | $ 2.9 |
Goodwill impairment charges |  | 1.9
Fair Value Measurements |  |
Intangible asset impairment charges | 2.9 |
Goodwill impairment charges |  | $ 1.9
Minimum | ASU 2016-12 |  |
Accounting Pronouncements |  |
Lease assets | 20.0 |
Lease liabilities | 20.0 |
Maximum | ASU 2016-12 |  |
Accounting Pronouncements |  |
Lease assets | 25.0 |
Lease liabilities | $ 25.0 |
Buildings and improvements | Minimum |  |
Property and Equipment |  |
Estimated useful lives | 5 years |
Buildings and improvements | Maximum |  |
Property and Equipment |  |
Estimated useful lives | 40 years |
Warehouse equipment | Minimum |  |
Property and Equipment |  |
Estimated useful lives | 3 years |
Warehouse equipment | Maximum |  |
Property and Equipment |  |
Estimated useful lives | 12 years |
Furniture, fixtures and leasehold improvements | Minimum |  |
Property and Equipment |  |
Estimated useful lives | 1 year |
Furniture, fixtures and leasehold improvements | Maximum |  |
Property and Equipment |  |
Estimated useful lives | 12 years |
Vehicles | Minimum |  |
Property and Equipment |  |
Estimated useful lives | 2 years |
Vehicles | Maximum |  |
Property and Equipment |  |
Estimated useful lives | 5 years |

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