Summary of Significant Accounting Policies - Useful lives of real estate assets and liabilities (Details)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Land improvements [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Asset estimated useful life	15 years
Land improvements [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Asset estimated useful life	38 years 1 month 6 days
Building and improvements [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Asset estimated useful life	3 years 3 months 18 days
Building and improvements [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Asset estimated useful life	39 years
Lease intangibles (including ground lease intangibles) [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Asset estimated useful life	1 year
Intangible asset useful life	1 year
Lease intangibles (including ground lease intangibles) [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Asset estimated useful life	93 years 1 month 6 days
Intangible asset useful life	93 years 1 month 6 days
Personal property [Member]
Property, Plant and Equipment [Line Items]
Asset estimated useful life		1 year 10 months 24 days
Personal property [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Asset estimated useful life	1 year 10 months 24 days
Personal property [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Asset estimated useful life	15 years 9 months 18 days