Variable Interest Entities (Details) (USD $)	3 Months Ended
	Mar. 31, 2013 Investment Entity Venture Asset	Mar. 31, 2013 Cerritos [Member]	Mar. 31, 2013 Cerritos [Member] Mortgage Debt Notes A [Member]	Mar. 31, 2012 Cerritos [Member] Mortgage Debt Notes B [Member]	Mar. 31, 2013 1515 Market Street Loan Modification [Member]	Mar. 31, 2012 1515 Market Street Loan Modification [Member]
Variable Interest Entity [Line Items]
Land and building		$ 21,396,000				$ 43,143,000
Net of accumulated depreciation		369,000				142,000
Lease intangibles		3,457,000				16,832,000
Accumulated amortization		300,000				368,000
Mortgage debt			$ 23,174,000	$ 860,000
Trust acquired equity					49.00%
Variable Interest Entities (Textual) [Abstract]
Variable interest entity ownership percentage	100.00%
Number of identified consolidated variable interest entities	2
Identified investments	11
Investments with no equity at risk	7
Number of additional entities	4
Unconsolidated joint venture	11
Number of assets identified as variable interests in variable interest entities	4
Investments lacking the right to receive returns	1