Shareholder Rights Plan - Narrative (Details) - Stockholder Rights Plan	Feb. 15, 2018 $ / shares shares
Class of Warrant or Right [Line Items]
Stockholder rights plan, ownership triggering threshold	10.00%
Number of securities, representing the right to purchase one half of a share of Luby’s common stock, upon specified terms and conditions (in shares) | shares	0.5
Exercise price of rights (in usd per share)	$ 12.00
Redemption rights per shares (in usd per share)	$ 0.01
Harris J. Pappas And Affiliates
Class of Warrant or Right [Line Items]
Stockholder rights plan, ownership triggering threshold	35.50%
Christopher J. Pappas And Affiliates
Class of Warrant or Right [Line Items]
Stockholder rights plan, ownership triggering threshold	35.50%