Components of Rental Income and Expense (Details Textual) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Components of Rental Income and Expense (Textual) [Abstract]
Recognition of straight-line rents	$ 2.2	$ 1.9	$ 6.2	$ 3.3
Recognition of amortization of above and below market leases		$ (0.9)	$ (0.7)	$ (1.6)