Investments in Unconsolidated Entities - Summary of Company's Investments in Unconsolidated Entities (Detail)	3 Months Ended
	Mar. 31, 2021 ft² Property
Income Statement Equity Method Investments [Line Items]
Number of Properties	25
Total GLA | ft²	3,968,600
Brookfield Properties Retail I [Member]
Income Statement Equity Method Investments [Line Items]
Seritage % Ownership	50.00%
Number of Properties	4
Total GLA | ft²	520,400
Brookfield Properties Retail II [Member]
Income Statement Equity Method Investments [Line Items]
Seritage % Ownership	50.00%
Number of Properties	3
Total GLA | ft²	474,100
The Macerich Company [Member]
Income Statement Equity Method Investments [Line Items]
Seritage % Ownership	50.00%
Number of Properties	7
Total GLA | ft²	1,266,600
Simon Property Group Inc [Member]
Income Statement Equity Method Investments [Line Items]
Seritage % Ownership	50.00%
Number of Properties	5
Total GLA | ft²	872,200
Invesco Real Estate [Member]
Income Statement Equity Method Investments [Line Items]
Seritage % Ownership	50.00%
Number of Properties	1
Total GLA | ft²	103,000
Invesco Real Estate II [Member]
Income Statement Equity Method Investments [Line Items]
Seritage % Ownership	50.00%
Number of Properties	1
Total GLA | ft²	226,200
First Washington Realty [Member]
Income Statement Equity Method Investments [Line Items]
Seritage % Ownership	50.00%
Number of Properties	1
Total GLA | ft²	163,700
Greenberg Gibbons [Member]
Income Statement Equity Method Investments [Line Items]
Seritage % Ownership	50.00%
Number of Properties	1
Total GLA | ft²	160,200
RD Management [Member]
Income Statement Equity Method Investments [Line Items]
Seritage % Ownership	50.00%
Number of Properties	1
New Mark Merrilll Companies And Other Entities [Member]
Income Statement Equity Method Investments [Line Items]
Seritage % Ownership	20.00%
Number of Properties	1
Total GLA | ft²	182,200