Fair Value Measures (Narrative) (Details) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2015 USD ($) property	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairments		$ 85,341	$ 3,855
Number of properties noted to have estimated sales price less than carrying amount | property	161
Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Length of time for properties more likely than not of being disposed	12 months
Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Length of time for properties more likely than not of being disposed	24 months
Reported Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying value of real estate assets deemed to be impaired		319,300	8,200
Estimated fair value of real estate assets deemed to be impaired	$ 234,000	$ 234,000	$ 4,300