Fair Value Measures (Impairment Charges by Asset Class) (Details)	3 Months Ended
	Mar. 31, 2016 USD ($) property	Mar. 31, 2015 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Properties impaired | property	125
Total impairment loss	$ 160,517,000	$ 0
Investment in Real Estate Assets, Net [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total impairment loss	160,721,000
Below-Market Lease Liabilities, Net [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total impairment loss	$ (204,000)