Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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Share Based Compensation - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Jul. 07, 2015
Time Based Restricted Shares and Share Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years
Restricted Share [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation costs	$ 9.2	$ 6.6
Unrecognized compensation costs, weighted average expected recognition period	1 year 10 months 24 days	1 year 7 months 6 days
Restricted Share [Member] \| General and Administrative Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense recognized	$ 1.2	$ 1.5
Seritage Growth Properties 2015 Share Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares of common stock reserved for issuance			3,250,000