Investment in Real Estate - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2013 sqft Parcels Property	Mar. 31, 2012 Property	Dec. 31, 2012 Property
Real Estate Investments [Line Items]
Number of Land Parcels Acquired	2
Purchase price of land parcels	$ 9,334
Number of industrial properties sold	4	3	28
Gross leasable area (GLA) of industrial properties sold	200,000
Number of Land Parcels Sold	2
Proceeds from the sales	11,187
Net loss on sale of properties	2,812	(6,199)
Number Of Sold Land Parcels Included In Continuing Operations	2
Number of industrial properties held for sale	4
Gross leasable area (GLA) of industrial properties held for sale	800,000
Number Of Land Parcels Held For Sale	1
Impairment reversal of industrial properties		304
Notes receivable outstanding	41,065		41,201
Net discount of notes receivable outstanding	239		255
Fair value of notes receivable	$ 43,267		$ 44,783
Discontinuing Operations [Member]
Real Estate Investments [Line Items]
Number of Sold Properties Included in Discontinued Operations	4