Related Party Transactions Excluded Properties and Businesses (Details)	Dec. 31, 2014 office_and_property
Retail Site [Member] | Manhattan [Member]
Related Party Transaction [Line Items]
Number of properties	4
Office Building [Member]
Related Party Transaction [Line Items]
Number of properties	14
Office Building [Member] | Manhattan [Member]
Related Party Transaction [Line Items]
Number of properties	9
Malkin Group [Member] | Mezzanine and Senior Equity Funds [Member]
Related Party Transaction [Line Items]
Number of interests owned	6
Malkin Group [Member] | Industrial Funds [Member]
Related Party Transaction [Line Items]
Number of interests owned	3
Malkin Group [Member] | Residential Property Manager [Member]
Related Party Transaction [Line Items]
Number of properties	5
Number of interests owned	5
Malkin Group [Member] | Multi-family Property [Member] | Greenwich, Connecticut [Member]
Related Party Transaction [Line Items]
Number of properties	5
Malkin Group [Member] | Retail Site [Member] | Greenwich, Connecticut [Member]
Related Party Transaction [Line Items]
Number of properties	3
Malkin Group [Member] | Retail Site [Member] | Manhattan [Member]
Related Party Transaction [Line Items]
Number of properties	2
Malkin Group [Member] | Former Post Office [Member] | Greenwich, Connecticut [Member]
Related Party Transaction [Line Items]
Number of properties	1
Malkin Group [Member] | Office Building [Member] | Manhattan [Member]
Related Party Transaction [Line Items]
Number of properties	1