Investment in Real Estate - Fair Value Measurements on Non-Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended			9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013		Sep. 30, 2014	Sep. 30, 2013
Fair Value Assets Measured On Nonrecurring Basis [Line Items]
Total Impairment	$ 0	$ (1,047)		$ 0	$ (1,047)	[1]
Fair Value, Measurements, Nonrecurring
Fair Value Assets Measured On Nonrecurring Basis [Line Items]
Operating Property Not Held for Sale		6,875	[1]		6,875	[1]
Fair Value, Measurements, Nonrecurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value Assets Measured On Nonrecurring Basis [Line Items]
Operating Property Not Held for Sale		0			0
Fair Value, Measurements, Nonrecurring | Significant Other Observable Inputs (Level 2)
Fair Value Assets Measured On Nonrecurring Basis [Line Items]
Operating Property Not Held for Sale		0			0
Fair Value, Measurements, Nonrecurring | Unobservable Inputs (Level 3)
Fair Value Assets Measured On Nonrecurring Basis [Line Items]
Operating Property Not Held for Sale		$ 6,875	[1]		$ 6,875	[1]

[1] Excludes industrial properties for which impairment of $1,605 was recorded during the nine months ended September 30, 2013 since the related assets were sold or recorded at carrying value, which is lower than estimated fair value at September 30, 2013.