Fair Value Measures (Impairment Charges by Asset Class) (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2016 USD ($) property	Sep. 30, 2015 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Properties impaired | property	139
Total impairment loss	$ 176,214	$ 85,300
Number of properties disposed of | property	35
Investment in Real Estate Assets, Net [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total impairment loss	$ 176,635
Below-Market Lease Liabilities, Net [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total impairment loss	$ (421)