Employee Benefit Plans (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Aug. 25, 2012	Aug. 27, 2011	Aug. 28, 2010
Defined Benefit Plan Disclosure [Line Items]
Contributions charged to expense	$ 11,500	$ 10,600	$ 11,000
Supplemental Executive Retirement Plan (SERP) [Member]
Defined Benefit Plan Disclosure [Line Items]
Contributions charged to expense	1,800	1,700	1,500
Components of net periodic benefit cost [Abstract]
Service cost	512	486	391
Interest cost	858	764	702
Expected return on assets	0	0	0
Amortization of prior service cost	368	368	368
Amortization of unrecognized loss	107	131	54
Other events	0	0	0
Net periodic benefit cost	1,845	1,749	1,515
Change in benefit obligation [Rollforward]
Project benefit obligation, beginning of year	14,944	13,987
Service cost	512	486	391
Interest cost	858	764	702
Actuarial (gain) loss	622	98
Benefits paid	(537)	(391)
Settlements	0	0
Project benefit obligation, end of year	16,399	14,944	13,987
Change in plan assets [Rollforward]
Fair value of plan assets, beginning of year	0	0
Actual return on plan assets	0	0
Employer contributions	0	0
Benefits paid	0	0
Settlements	0	0
Fair value of plan assets, end of year	0	0	0
Funded status (net amount recognized):	(16,399)	(14,944)
Accumulated benefit obligations [Abstract]
Accumulated benefit obligations	12,900	11,600
Amounts recognized in balance sheet [Abstract]
Deferred tax assets	1,648	1,716
Accrued liabilities	16,399	14,944
Accumulated other comprehensive loss	(2,633)	(2,742)
Amounts recognized in other accumulated other comprehensive income (loss), before tax [Abstract]
Net actuarial loss	(1,694)	(1,577)
Unrecognized prior service cost	(939)	(1,165)
Total	(2,633)	(2,742)
Weighted average assumptions used in calculating benefit obligation [Abstract]
Discount rate (in hundredths)	3.60%	4.90%
Rate of compensation increase (in hundredths)	5.00%	5.00%
Defined benefit plan, weighted average assumptions used in calculating net periodic benefit cost [Abstract]
Discount rate (in hundredths)	4.90%	4.80%	5.70%
Expected return on plan assets (in hundredths)	0.00%	0.00%	0.00%
Rate of compensation increase (in hundredths)	5.00%	5.00%	5.00%
Unifirst Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Contributions charged to expense	300	300	300
Textilease Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Contributions charged to expense	100	100	100
Pension Plans, Defined Benefit [Member]
Components of net periodic benefit cost [Abstract]
Service cost	152	149	136
Interest cost	322	328	351
Expected return on assets	(199)	(202)	(191)
Amortization of prior service cost	62	62	62
Amortization of unrecognized loss	65	78	20
Other events	43	65	0
Net periodic benefit cost	445	480	378
Change in benefit obligation [Rollforward]
Project benefit obligation, beginning of year	7,372	7,339
Service cost	152	149	136
Interest cost	322	328	351
Actuarial (gain) loss	937	114
Benefits paid	(299)	(319)
Settlements	(183)	(239)
Project benefit obligation, end of year	8,301	7,372	7,339
Change in plan assets [Rollforward]
Fair value of plan assets, beginning of year	5,145	5,263
Actual return on plan assets	202	205
Employer contributions	249	235
Benefits paid	(299)	(319)
Settlements	(183)	(239)
Fair value of plan assets, end of year	5,114	5,145	5,263
Funded status (net amount recognized):	(3,187)	(2,227)
Accumulated benefit obligations [Abstract]
Accumulated benefit obligations	8,300	7,400
Amounts recognized in balance sheet [Abstract]
Deferred tax assets	1,089	795
Accrued liabilities	3,187	2,227
Accumulated other comprehensive loss	(1,740)	(1,269)
Amounts recognized in other accumulated other comprehensive income (loss), before tax [Abstract]
Net actuarial loss	(1,445)	(936)
Unrecognized prior service cost	(295)	(333)
Total	$ (1,740)	$ (1,269)
Weighted average assumptions used in calculating benefit obligation [Abstract]
Discount rate (in hundredths)	3.30%	4.60%
Rate of compensation increase (in hundredths)	0.00%	0.00%
Defined benefit plan, weighted average assumptions used in calculating net periodic benefit cost [Abstract]
Discount rate (in hundredths)	4.60%	4.70%	5.80%
Expected return on plan assets (in hundredths)	4.00%	4.00%	4.00%
Rate of compensation increase (in hundredths)	0.00%	0.00%	0.00%