Acquisitions and Dispositions (Summary of Significant Assumptions Utilized in Estimates) (Details) (USD $)	9 Months Ended
	Sep. 30, 2012 months
Minimum [Member]
Fair Value Inputs, Discount Rate	7.19%
Fair Value Inputs, Cap Rate	5.75%
Lease-up period (months)	9
Minimum [Member] | Industrial [Member]
Rental rate per square foot	2.75
Minimum [Member] | Medical Office [Member]
Rental rate per square foot	16.00
Maximum [Member]
Fair Value Inputs, Discount Rate	8.78%
Fair Value Inputs, Cap Rate	7.40%
Lease-up period (months)	19
Maximum [Member] | Industrial [Member]
Rental rate per square foot	7.62
Maximum [Member] | Medical Office [Member]
Rental rate per square foot	26.14