Investment in Real Estate - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended		12 Months Ended
	Jun. 30, 2013 Property Parcels sqft	Jun. 30, 2012 Property	Dec. 31, 2012 Property
Real Estate Investments [Line Items]
Number of industrial properties acquired	1
Square footage of real estate property acquired	500,000
Purchase price of acquisitions	$ 46,463
Number of industrial properties sold	12	6	26
Gross leasable area (GLA) of industrial properties sold	1,300,000
Number of land parcels sold	2
Gross proceeds from the sale of industrial properties and land parcels	52,598
Net gain on sale of properties and land parcels	10,669	7,614
Number of sold land parcels included in continuing operations	2
Number of industrial properties held for sale	2
Gross leasable area (GLA) of industrial properties held for sale	100,000
Impairment reversal of industrial properties		93
Notes receivable outstanding	40,938		41,201
Net discount of notes receivable outstanding	223		255
Fair value of notes receivable	$ 42,144		$ 44,783
Discontinuing Operations [Member]
Real Estate Investments [Line Items]
Number of sold properties included in discontinued operations	12