Fair Value Measurements - Assets at Fair Value on Nonrecurring Basis (Details) - USD ($)
$ in Thousands
 3 Months Ended 12 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total Impairment Charges $ (2,234) $ (1,911)  
Fair Value, Measurements, Nonrecurring      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Long-lived assets held and used, Dispositions     $ 0
Lease intangible assets, Dispositions 0   0
Long-lived assets held for sale, Dispositions 0   (26,721)
Long-lived assets held and used, Impairment Charges     (20,679)
Lease intangible assets, Impairment Charges (615)   4,317
Long-lived assets held for sale, Impairment Charges (1,619)   (21,653)
Total Impairment Charges (2,234)   (38,015)
Fair Value, Measurements, Nonrecurring | Level 1      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Long-lived assets held and used     0
Lease intangible assets 0   0
Long-lived assets held for sale 0   0
Fair Value, Measurements, Nonrecurring | Level 2      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Long-lived assets held and used     0
Lease intangible assets 0   0
Long-lived assets held for sale 0   0
Fair Value, Measurements, Nonrecurring | Level 3      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Long-lived assets held and used     37,278
Lease intangible assets 0   10,013
Long-lived assets held for sale 4,495   92,679
Fair Value | Fair Value, Measurements, Nonrecurring      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Long-lived assets held and used     37,278
Lease intangible assets 0   10,013
Long-lived assets held for sale $ 4,495   $ 65,958