Impairment of Long-Lived Assets, Discontinued Operations, Property Held for Sale and Store Closings - Narrative (Details)	3 Months Ended			6 Months Ended		12 Months Ended
	Mar. 14, 2018 USD ($) location property restaurant	Mar. 15, 2017 USD ($) property	Nov. 18, 2009 location	Mar. 14, 2018 USD ($) location property restaurant	Mar. 15, 2017 USD ($) location property	Aug. 30, 2017 USD ($) property restaurant
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Asset impairment charges	$ 1,407,000	$ 5,963,000		$ 2,252,000	$ 6,250,000
Number of restaurants with impaired assets | location				7	4
Number of restaurants with impaired goodwill | location				2	6
Lease termination costs				$ 600,000
Number of restaurants with lease termination costs | location				5
Net loss (gain) on disposition of property and equipment	(204,000)	$ 329,000		$ 18,000	$ 414,000
Number of restaurants related to asset retirements | location				6
Number of restaurants related to net gain (loss) on disposition | property				2
Assets of disposal group, number | property				4		4
Property and equipment, net	169,539,000			$ 169,539,000		$ 172,814,000
Property held for sale	2,900,000			2,900,000		3,400,000
Accrued lease termination expense	$ 1,000,000			$ 1,000,000		$ 500,000
Company-owned restaurants
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of restaurants | restaurant	160			160		167
Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of restaurants | property	1			1
Impairment of leasehold				$ 0
Discontinued Operations | Company-owned restaurants
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Property and equipment, net	$ 1,900,000			$ 1,900,000
Cheeseburger in Paradise
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of restaurants | location	3			3
Cheeseburger in Paradise | Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of restaurants | location	0			0
Lubys Cafetria | Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Assets of disposal group, number | location			24
Discontinued Operations, Held-for-sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of restaurants | property	3	13		3	13
Discontinued Operations, Held-for-sale | Lubys Cafetria | Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of restaurants | location	1			1
Discontinued Operations, Disposed of by Means Other than Sale, Abandonment
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Asset impairment charges				$ 700,000
Number of restaurants | restaurant	7			7
Newer Properties | Minimum
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Time span for future cash flow				20 years
Newer Properties | Maximum
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Time span for future cash flow				25 years
Older Properties | Minimum
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Time span for future cash flow				5 years
Older Properties | Maximum
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Time span for future cash flow				10 years