Discontinued Operations (Details) (USD $)	3 Months Ended		9 Months Ended		0 Months Ended		9 Months Ended			0 Months Ended		9 Months Ended		1 Months Ended
	Sep. 30, 2013 sqft	Sep. 30, 2012	Sep. 30, 2013 sqft	Sep. 30, 2012	Mar. 20, 2013 Atrium at Stoneridge sqft		Sep. 30, 2013 Atrium at Stoneridge sqft		Sep. 30, 2013 Waterstone sqft	Jul. 10, 2013 Waterstone and Meridian Property sqft	Jul. 17, 2013 Bank of America Plaza	Sep. 30, 2013 Bank of America Plaza sqft	Oct. 07, 2013 Subsequent Event Carmel Crossing sqft	Oct. 31, 2013 Subsequent Event Lakewood II sqft	Oct. 31, 2013 Parent Subsequent Event Lakewood II
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gross sales price of assets sold					$ 3,100,000
Gain on sale of real estate from discontinued operations	11,545,000	995,000	12,087,000	9,767,000			542,000	[1]	40,000		11,500,000	11,450,000		5,900,000	1,800,000
Net proceeds from the sale					3,000,000
Area of real estate property (in square feet)	640,000		640,000		108,000	[1]	108,000	[1]	93,000			436,000
Date of Sale							Mar. 20, 2013	[1]	Jul. 10, 2013			Jul. 17, 2013
Number of properties under agreement to sell										2
Gross sales price of assets under agreement to sell										10,200,000	42,800,000		37,500,000	10,600,000
Impairment loss on assets to be disposed of										4,600,000
Proceeds from sale of property										$ 9,500,000	$ 40,800,000			$ 3,100,000
Area of real estate property held for sale (in sqf)										190,000			326,000	123,000

[1] Total gain on the sale of real estate in discontinued operations recognized during the nine months ended September 30, 2013 was $12.1 million.