Investment in Real Estate - Property Previously Held For Sale (Details) ft² in Thousands	Mar. 31, 2018 ft²
Property Held for Sale \| Class A Office Property and Health Club Honolulu \| Office Building
Property Previously Held-for-sale [Line Items]
Area of real estate property previously held for sale (sqft)	80

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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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration