Investment in Real Estate - Quantitative Information About Level 3 Fair Value Measurements (Details) (Unobservable Inputs (Level 3), Third Party Pricing [Member], USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013 Property sqft		Jun. 30, 2012 sqft Property
Unobservable Inputs (Level 3) | Third Party Pricing [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Number of industrial properties	4		5
Gross leaseable area	300,000		1,800,000
Fair value of property	$ 6,993	[1]	$ 24,069	[1]

[1] (A)The fair value for the properties is based upon the value of a third party purchase contract or letter of intent, which is subject to our corroboration for reasonableness.