Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Aug. 26, 2017 USD ($) Store Product Vendor Branches $ / shares shares	Aug. 27, 2016 USD ($) shares	Aug. 29, 2015 USD ($) shares	Aug. 30, 2014 USD ($)
Significant Accounting Policies [Line Items]
Number of stores with commercial sales program | Store	4,592
Description of reporting periods	Fiscal Year The Company's fiscal year consists of 52 or 53 weeks ending on the last Saturday in August. Fiscal 2017, fiscal 2016 and fiscal 2015 represented 52 weeks.
Cash and cash equivalents	$ 293,270,000	$ 189,734,000	$ 175,309,000	$ 124,485,000
Allowances for uncollectible accounts	5,900,000	7,400,000
Unrecorded adjustment for LIFO value in excess of replacement value	414,900,000	364,100,000
Impairment loss of long lived assets	0
Deferred rent	$ 130,200,000	121,700,000
Measure of income tax benefit for uncertain income tax positions	More than 50%
Advertising expense, net of vendor promotional funds	$ 93,100,000	98,300,000	98,000,000
Vendor promotional funds, which reduced advertising expense	$ 28,300,000	21,400,000	22,000,000
Limited warranty period, minimum period (Days)	30 days
Products accounted for total revenues	One class of similar products accounted for approximately 11 percent of the Company's total revenues,No other class of similar products accounted for 10 percent or more of total revenues
Products accounted for total purchases	One vendor supplied approximately 10 percent of the Company's total purchases.No other individual vendor provided more than 10 percent of total purchases.
Increase of earning per share | $ / shares	$ 0.81
Effective tax rate basis point	1.62%
Tax benefit to earning per share | $ / shares	$ 1.08
Tax reduction to earning per share | $ / shares	$ 0.27
Excess tax benefit		$ 63,700,000	$ 47,900,000
Minimum [Member]
Significant Accounting Policies [Line Items]
Amortization of intangible assets	3 years
Maximum [Member]
Significant Accounting Policies [Line Items]
Amortization of intangible assets	10 years
Interamerican Motor Corporation [Member]
Significant Accounting Policies [Line Items]
Number of operating branches | Branches	26
Stock Options [Member]
Significant Accounting Policies [Line Items]
Anti-dilutive shares excluded from the computation of earnings per share | shares	620,915	329,900	778
Cash Equivalents [Member]
Significant Accounting Policies [Line Items]
Maturity period of investments	90 days or less
Settlement term of credit and debit card transaction	Less than five days
Credit and debit card receivables included within cash and cash equivalents	$ 48,300,000	$ 46,800,000
Product Concentration Risk [Member]
Significant Accounting Policies [Line Items]
Number of class of similar products accounted for approximately 11% of the company's total revenues | Product	1
Product Concentration Risk [Member] | Sales Revenue, Net [Member]
Significant Accounting Policies [Line Items]
Concentration risk percentage	11.00%
Supplier Concentration Risk [Member]
Significant Accounting Policies [Line Items]
Number of vendors accounted for approximately 10% of the company's total purchases | Vendor	1
Supplier Concentration Risk [Member] | Cost of Goods, Total [Member]
Significant Accounting Policies [Line Items]
Concentration risk percentage	10.00%
Buildings [Member] | Minimum [Member]
Significant Accounting Policies [Line Items]
Estimated useful lives	40 years
Buildings [Member] | Maximum [Member]
Significant Accounting Policies [Line Items]
Estimated useful lives	50 years
Building Improvements [Member] | Minimum [Member]
Significant Accounting Policies [Line Items]
Estimated useful lives	5 years
Building Improvements [Member] | Maximum [Member]
Significant Accounting Policies [Line Items]
Estimated useful lives	15 years
Equipment [Member] | Minimum [Member]
Significant Accounting Policies [Line Items]
Estimated useful lives	3 years
Equipment [Member] | Maximum [Member]
Significant Accounting Policies [Line Items]
Estimated useful lives	10 years
Stores in the United States Including Puerto Rico [Member]
Significant Accounting Policies [Line Items]
Number of stores | Store	5,465
Brazil [Member]
Significant Accounting Policies [Line Items]
Number of stores | Store	14
Mexico [Member]
Significant Accounting Policies [Line Items]
Number of stores | Store	524
Non-US [Member]
Significant Accounting Policies [Line Items]
Cash and cash equivalents	$ 148,400,000	$ 78,100,000