Earnings per Share - Reconciliation of Net Income (Loss) and Number of Common Shares Used in Computations of Basic Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Numerator - Basic and Diluted
Net loss	$ (66,987)	$ (10,933)
Net loss attributable to non-controlling interests	14,782	3,213
Preferred dividends	(1,225)	(1,225)
Net loss attributable to Seritage common shareholders	$ (53,430)	$ (8,945)
Denominator - Basic and Diluted
Weighted average Class A common shares outstanding	43,634	39,477
Weighted average Class A common shares outstanding - Diluted	43,634	39,477
Loss per share attributable to Class A common shareholders - Basic	$ (1.22)	$ (0.23)
Loss per share attributable to Class A common shareholders - Diluted	$ (1.22)	$ (0.23)
Class A Common Shares [Member]
Denominator - Basic and Diluted
Weighted average Class A common shares outstanding	43,634	39,477