Fair Value Measures (Impairment Charges by Asset Class) (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2016 USD ($) property	Jun. 30, 2015 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Properties impaired | property	132
Total impairment loss	$ 169,342	$ 85,300
Investment in Real Estate Assets, Net [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total impairment loss	169,762
Below-Market Lease Liabilities, Net [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total impairment loss	$ (420)