Impairment of Long-Lived Assets, Store Closings, Discontinued Operations and Property Held for Sale - Narrative (Details)	3 Months Ended		12 Months Ended
	Aug. 26, 2020 USD ($) restaurant property location lease	Nov. 18, 2009 location	Aug. 26, 2020 USD ($) lease restaurant property location	Aug. 28, 2019 USD ($) property location restaurant
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Impairment of goodwill			$ 320,000	$ 41,000
Net provision for asset impairments and restaurant closings			10,193,000	$ 5,603,000
Number of restaurants with assets impaired | location				9
Gain on lease termination			$ 3,300,000
Number of terminated leases | lease	17		17
Net gain on disposition of property and equipment	$ (8,700,000)		$ (11,557,000)	$ (12,832,000)
Gain on sale of properties				$ 12,900,000
Number of restaurants related to net gain (loss) on disposition, held for sale | property	5
Number of restaurants related to net gain (loss) on disposition, held for use | property	1
Number of restaurants with retired assets | location				3
Number of restaurants with goodwill impairment | location				1
Number of restaurants | property				7
Number of restaurant closings | restaurant				8
Reserve for restaurant closings				$ (200,000)
Pretax profit (loss) for disposal group			$ (500,000)	200,000
Company-owned restaurants
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of restaurants | restaurant	85		85
Continuing Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Impairment of goodwill			$ 0
Disposal Group, Disposed of by Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net provision for asset impairments and restaurant closings				5,600,000
Net gain on disposition of property and equipment			(11,557,000)	$ (12,832,000)
Gain on sale of properties			$ 8,400,000
Number of restaurants related to net gain (loss) on disposition, held for sale | property			7	2
Disposal Group, Disposed of by Sale | Facility Closing [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Impairment of goodwill			$ 300,000
Net provision for asset impairments and restaurant closings			10,200,000
Write off of right-of-use asset			$ 5,400,000
Number of restaurants suspended | restaurant	24		24
Impairment loss for property and equipment			$ 4,800,000
Number of restaurants with assets impaired | restaurant			24
Certain surplus equipment written down to fair value			$ 1,200,000
Restructuring related			1,800,000
Disposal Group, Disposed of by Means Other than Sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on sale of properties			$ 3,900,000
Number of restaurants related to net gain (loss) on disposition, held for use | property			2
Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Property held for sale	$ 1,715,000		$ 1,715,000	$ 1,813,000
Discontinued Operations, Held-for-sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of restaurants | property	1		1
Discontinued Operations, Held-for-sale | Company-owned restaurants
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Property held for sale	$ 1,700,000		$ 1,700,000
Disposal Group, Held-for-sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties | property	10		10	14
Property held for sale	$ 11,200,000		$ 11,200,000	$ 16,500,000
Discontinued Operations, Abandonment
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of leases abandoned | restaurant			18	11
Number of leases abandoned in period of abandonment | restaurant			24
Discontinued Operations, Disposed of by Means Other than Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of leases settled and terminated | lease			17
Minimum | Newer Properties
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Time span for which future cash flows are estimated			20 years
Minimum | Older Properties
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Time span for which future cash flows are estimated			5 years
Maximum | Newer Properties
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Time span for which future cash flows are estimated			25 years
Maximum | Older Properties
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Time span for which future cash flows are estimated			10 years
Luby's Cafeteria | Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of cafeterias classified as discontinued operations | location		24
Luby's Cafeteria | Discontinued Operations, Held-for-sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of restaurants | location	1		1