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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, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Real Estate [Abstract]
Total Revenues									$ 6,654	$ 19,418	$ 29,840
Property Expenses									(2,621)	(7,545)	(11,565)
Impairment of Real Estate									0	(2,652)	(1,121)
Depreciation and Amortization									(2,248)	(7,258)	(10,926)
Gain on Sale of Real Estate									23,796	32,657	12,758
Income from Discontinued Operations	$ 11,702	$ 12,073	$ 946	$ 860	$ 19,809	$ 3,559	$ 12,941	$ (1,689)	$ 25,581	$ 34,620	$ 18,986