Acquisitions and Dispositions (Summary of Significant Assumptions Utilized in Estimates) (Details) (USD $)	3 Months Ended
	Mar. 31, 2013 months
Minimum [Member]
Fair Value Inputs, Discount Rate	8.06%
Fair Value Inputs, Cap Rate	6.96%
Lease-up period (months)	12
Minimum [Member] | Industrial [Member]
Rental rate per square foot	2.95
Minimum [Member] | Medical Office [Member]
Rental rate per square foot	18.00
Maximum [Member]
Fair Value Inputs, Discount Rate	9.67%
Fair Value Inputs, Cap Rate	7.67%
Lease-up period (months)	24
Maximum [Member] | Industrial [Member]
Rental rate per square foot	2.95
Maximum [Member] | Medical Office [Member]
Rental rate per square foot	18.00