Subsequent Events (Details) (USD $)	3 Months Ended				0 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Apr. 03, 2014 Four Points Centre [Member] Properties Storey sqft	Apr. 03, 2014 Austin Joint Venture [Member] Four Points Centre [Member]	Apr. 03, 2014 Austin Joint Venture [Member] Brandywine Realty Trust [Member] Four Points Centre [Member]	Apr. 03, 2014 Austin Joint Venture [Member] DRA Advisors LLC [Member] Four Points Centre [Member]
Subsequent Event [Line Items]
Number of Real Estate Properties			2
Number of floors of a building			3
Net Rentable Space			192,396
Aggregate gross sales price of a joint venture					$ 41,500,000
Non-Recourse Debt				29,000,000
Amount Of Participant Contribution						5,900,000
Proceeds from Equity Method Investment, Dividends or Distributions	2,828,000	1,357,000			34,400,000
Payments to Acquire Equity Method Investments					5,900,000
Loss On Real Estate Venture Transactions, including real estate venture formation	$ (135,000)	$ 0			$ (200,000)