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Disposals of Properties and Assets Held for Sale (Details) - Disposed of by Sale
$ in Millions
9 Months Ended
Sep. 30, 2021
USD ($)
groundLease
Sep. 30, 2020
property
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]    
Number of ground lease properties | groundLease 17  
Gross proceeds from sale of ground lease property $ 42.0  
Net gain from sale of ground lease property $ 27.6  
Number of real estate properties | property   0