Investment in Office and Parking Properties - Schedule of Purchase Price Allocation for 2014 Purchases (Details) (USD $)	0 Months Ended
	Apr. 10, 2014	Dec. 31, 2014
2014 Acquisitions
Business Acquisition [Line Items]
Land		$ 146,602,000
Buildings		617,807,000
Tenant improvements		46,146,000
Lease commissions		17,575,000
Below market leases		(21,433,000)
Mortgage assumed		(18,251,000)	[1]
2014 Acquisitions | Lease In Place Value
Business Acquisition [Line Items]
Leases		47,070,000
2014 Acquisitions | Above Market Leases
Business Acquisition [Line Items]
Leases		10,272,000
2014 Acquisitions | Above and Below Market Leases
Business Acquisition [Line Items]
Leases		16,687,000
FLORIDA | Courvoisier Centre
Business Acquisition [Line Items]
Credits from seller	$ 5,300,000

[1] Mortgage debt assumed with the purchase of One Orlando Centre, One Congress Plaza and San Jacinto Center.