Component of Rental Income and Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating Leases, Income Statement, Lease Revenue [Abstract]
Recognition of straight-line rents	$ 1.9	$ 2.6	$ 7.2
Recognition of amortization of above and below market leases	$ 2.8	$ 2.4	$ (0.2)