Investment in Real Estate - Summary Regarding Industrial Properties Included in Discontinued Operations (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total Revenues									$ 8,701	$ 18,871	$ 25,318
Property Expenses									(3,660)	(7,589)	(10,601)
Impairment of Real Estate									(1,410)	(4,973)	(66,026)
Depreciation and Amortization									(1,612)	(4,473)	(10,306)
Interest Expense										(63)	(268)
Gain on Sale of Real Estate									12,665	20,419	11,092
Provision for Income Taxes										(1,246)
Income (Loss) from Discontinued Operations	$ 718	$ 5,478	$ 2,535	$ 5,953	$ 9,265	$ 6,134	$ 2,873	$ 2,674	$ 14,684	$ 20,946	$ (50,791)