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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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