Fair Value Measures (Narrative) (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
Impairment charges	$ 160,517,000	$ 0
Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount rates	7.50%
Capitalization rates	7.00%
Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount rates	9.00%
Capitalization rates	12.46%
Weighted Average [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount rates	8.10%
Capitalization rates	7.80%
Reported Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated fair value of real estate assets deemed to be impaired	$ 462,500,000