Goodwill and Intangibles - Additional Information (Detail) - USD ($)	4 Months Ended		12 Months Ended
	Aug. 26, 2017	Aug. 27, 2016	Aug. 26, 2017	Aug. 27, 2016	Aug. 29, 2015	Aug. 30, 2014
Finite Lived And Indefinite Lived Intangible Assets [Line Items]
Goodwill impairment charge	$ 0	$ 0
Accumulated goodwill impairment	18,300,000	18,300,000	$ 18,300,000	$ 18,300,000
Purchase of intangibles			0	10,000,000	$ 10,000,000
Amortization expense of intangible assets			8,500,000	8,700,000
Trade Names [Member] | AutoAnything's and Interamerican Motor Corporation [Member]
Finite Lived And Indefinite Lived Intangible Assets [Line Items]
Impairment charge	0	0
Accumulated impairment	$ 4,100,000	$ 4,100,000	$ 4,100,000	4,100,000
Customer Relationships [Member]
Finite Lived And Indefinite Lived Intangible Assets [Line Items]
Purchase of intangibles				$ 10,000,000	$ 10,000,000
Customer Relationship and Technology Assets [Member]
Finite Lived And Indefinite Lived Intangible Assets [Line Items]
Purchase of intangibles						$ 30,200,000