Variable Interest Entities - Additional Information (Detail) (USD $)	6 Months Ended
	Jun. 30, 2013 Investment Entity Venture Assets
Variable Interest Entity [Line Items]
Number of identified consolidated variable interest entities	2
Variable interest entity ownership percentage	100.00%
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
Cerritos [Member]
Variable Interest Entity [Line Items]
Land and building	$ 22,304,000
Net of accumulated depreciation	597,000
Lease intangibles	3,375,000
Accumulated amortization	464,000
Cerritos [Member] | Mortgage Debt Notes A [Member]
Variable Interest Entity [Line Items]
Mortgage debt	23,163,000
Cerritos [Member] | Mortgage Debt Notes B [Member]
Variable Interest Entity [Line Items]
Mortgage debt	845,000
1515 Market Street Loan Modification [Member]
Variable Interest Entity [Line Items]
Land and building	43,142,000
Net of accumulated depreciation	364,000
Lease intangibles	16,982,000
Accumulated amortization	972,000
Mortgage debt	$ 42,922,000
Trust acquired equity	49.00%