Annual report pursuant to Section 13 and 15(d)

Recent Transactions (Land Impairments) (Narrative) (Details)

v3.19.3.a.u2
Recent Transactions (Land Impairments) (Narrative) (Details)
$ in Millions
12 Months Ended
Dec. 31, 2018
USD ($)
property
Dec. 31, 2019
property
Property, Plant and Equipment [Line Items]    
Land impairments | $ $ 24.6  
Conshohocken And Bala Cynwyd, Pennsylvania [Member]    
Property, Plant and Equipment [Line Items]    
Number of real estate properties   2
Conshohocken And Bala Cynwyd, Pennsylvania [Member] | Land [Member]    
Property, Plant and Equipment [Line Items]    
Number of real estate properties 2