Fair Value Measurements - Schedule of Assets at Fair Value on Nonrecurring Basis (Details) - USD ($)
$ in Thousands
3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2016
Sep. 30, 2015
Sep. 30, 2016
Sep. 30, 2015
Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Impairment of other assets $ (22) $ (57) $ (21) $ (153)  
Total impairment charges (15,407) $ (21,027) (41,396) $ (57,032)  
Fair Value, Measurements, Nonrecurring          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Long-lived assets held and used 11,525   11,525   $ 60,298
Lease intangible assets 5,059   5,059   3,843
Other assets 0   0   0
Long-lived assets held for sale 9,746   9,746   15,957
Long-lived assets held and used, dispositions 0   0   (3,207)
Lease intangible assets, dispositions 0   0   0
Other assets, dispositions 0   0   0
Long-lived assets held for sale, dispositions (33,668)   (33,668)   (33,563)
Impairment of long-lived assets held and used     (18,044)   (51,002)
Impairment of intangible assets     (8,403)   (3,825)
Impairment of other assets     301   (324)
Impairment of long-lived assets held for sale     (15,250)   (15,578)
Total impairment charges     (41,396)   (70,729)
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   0   0
Lease intangible assets 0   0   0
Other assets 0   0   0
Long-lived assets held for sale 0   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   0   0
Lease intangible assets 0   0   0
Other assets 0   0   0
Long-lived assets held for sale 0   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 11,525   11,525   63,505
Lease intangible assets 5,059   5,059   3,843
Other assets 0   0   0
Long-lived assets held for sale 43,414   43,414   49,520
Retail | Fair Value, Measurements, Nonrecurring          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Long-lived assets held and used 7,772   7,772   29,626
Long-lived assets held and used, dispositions 0   0   (3,207)
Impairment of long-lived assets held and used     (12,612)   (20,727)
Retail | 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   0   0
Retail | 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   0   0
Retail | 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 7,772   7,772   32,833
Industrial | Fair Value, Measurements, Nonrecurring          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Long-lived assets held and used 3,753   3,753   9,598
Long-lived assets held and used, dispositions 0   0   0
Impairment of long-lived assets held and used     (5,432)   (16,182)
Industrial | 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   0   0
Industrial | 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   0   0
Industrial | 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 $ 3,753   $ 3,753   9,598
Office | Fair Value, Measurements, Nonrecurring          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Long-lived assets held and used         21,074
Long-lived assets held and used, dispositions         0
Impairment of long-lived assets held and used         (14,093)
Office | 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
Office | 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
Office | 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         $ 21,074