Investment in Office and Parking Properties - Narrative (Details)	Sep. 30, 2015 property state
Real Estate Properties [Line Items]
Number of states in which office properties are located \| state	6
Office Building
Real Estate Properties [Line Items]
Number of office and parking properties	35

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration