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		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Numerator - Basic and Diluted
Net loss	$ (142,083)	$ (95,304)	$ (209,070)	$ (106,237)
Net loss attributable to non-controlling interests	31,328	22,464	46,110	25,677
Preferred dividends	(1,225)	(1,225)	(2,450)	(2,450)
Net loss attributable to Seritage common shareholders	$ (111,980)	$ (74,065)	$ (165,410)	$ (83,010)
Denominator - Basic and Diluted
Weighted average Class A common shares outstanding	43,677	42,772	43,656	41,134
Weighted average Class A common shares outstanding - Diluted	43,677	42,772	43,656	41,134
Loss per share attributable to Class A common shareholders - Basic	$ (2.56)	$ (1.73)	$ (3.79)	$ (2.02)
Loss per share attributable to Class A common shareholders - Diluted	$ (2.56)	$ (1.73)	$ (3.79)	$ (2.02)
Class A Common Shares [Member]
Denominator - Basic and Diluted
Weighted average Class A common shares outstanding	43,677	42,772	43,656	41,134