Real Estate (Significant Acquisitions and Disposition) (Details) (USD $)	3 Months Ended	12 Months Ended						12 Months Ended					0 Months Ended						12 Months Ended
	Sep. 30, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 Darien [Member]	Apr. 03, 2013 Darien [Member] sqft	Sep. 30, 2013 ResidentialPropertyAdjacentToSantanaRow [Member]	Dec. 31, 2012 EastBayBridge [Member]	Dec. 21, 2012 EastBayBridge [Member] sqft	Dec. 21, 2012 Crossroads (Office Building) [Member] sqft	Dec. 21, 2012 EastBayBridge [Member]	Dec. 30, 2011 Plaza El Segundo [Member]	Sep. 10, 2013 Forest Hills [Member]	Apr. 05, 2013 Shirlington [Member]	Jul. 22, 2013 Fifth Avenue [Member]	Oct. 02, 2013 LandParcelAdjacenttoAssemblyRow [Member] acre	Dec. 19, 2013 Land Contiguous with Montrose Crossing [Member]	Dec. 19, 2013 Montrose Crossing [Member]	Dec. 31, 2013 Crossroads (Office Building) [Member]
Real Estate Investments [Line Items]
Mortgage loan face amount											$ 62,900,000
Leasable area (square feet)						95,000			438,000	37,000
Business Acquisition, Purchase Price Allocation, Amortizable Intangible Assets						100,000			900,000
Business Acquisition Purchase Price Allocation Amortizable Intangible Below Market Lease Liabilities						1,800,000			47,800,000
Number of Real Estate Properties Acquired							3
NumberofResidentialUnits							47
Acquisition costs					200,000			900,000
Proceeds from sale of buildings													20,400,000	6,500,000	15,300,000				2,500,000
Gain (Loss) on Sale of Properties, Net of Applicable Income Taxes		4,994,000	11,860,000	0										5,000,000
Discontinued Operation, Gain (Loss) on Disposal of Discontinued Operation, Net of Tax	23,900,000	23,861,000	0	15,075,000									13,200,000		10,700,000
Area of Land																11.8
Land Acquisition Purchase Price																18,000,000	10,500,000
Business Acquisition, Percentage of Voting Interests Acquired												48.20%						89.90%
Land Acquisition Our Share of Purchase Price																	9,400,000
Business Acquisition Purchase Price						47,300,000	9,000,000		116,600,000	2,500,000
Long-term Debt, Fair Value											$ 67,600,000