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		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Numerator - Basic and Diluted
Net loss	$ (3,481)	$ (26,349)	$ (212,551)	$ (132,586)
Net loss attributable to non-controlling interests	42	5,815	46,152	31,492
Preferred dividends	(1,225)	(1,225)	(3,675)	(3,675)
Net loss attributable to Seritage common shareholders	$ (4,664)	$ (21,759)	$ (170,074)	$ (104,769)
Denominator - Basic and Diluted
Weighted average Class A common shares outstanding	55,361	43,631	47,600	41,976
Weighted average Class A common shares outstanding - Diluted	55,361	43,631	47,600	41,976
Loss per share attributable to Class A common shareholders - Basic	$ (0.08)	$ (0.50)	$ (3.57)	$ (2.50)
Loss per share attributable to Class A common shareholders - Diluted	$ (0.08)	$ (0.50)	$ (3.57)	$ (2.50)
Class A Common Shares [Member]
Denominator - Basic and Diluted
Weighted average Class A common shares outstanding	55,361	43,631	47,600	41,976