Property Dispositions - Results of Operations (Details) - USD ($)
$ in Thousands
3 Months Ended 12 Months Ended
Dec. 31, 2016
Sep. 30, 2016
Jun. 30, 2016
Mar. 31, 2016
Dec. 31, 2015
Sep. 30, 2015
Jun. 30, 2015
Mar. 31, 2015
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Disposal Group, Including Discontinued Operation, Income Statement Disclosures                      
Revenues $ 113,875 $ 110,076 $ 109,185 $ 107,226 $ 110,328 $ 108,202 $ 109,667 $ 98,750 $ 440,362 $ 426,947 $ 396,706
Expenses $ (60,118) $ (87,442) $ (60,037) $ (56,205) $ (56,736) $ (54,253) $ (53,795) $ (54,108) (263,802) (218,892) (221,226)
Gain on sale of real estate, net of tax                 132,858 2,197 13,338
Provision for income taxes                 (8,477) (8,885) (10,725)
Income before gain on sale of real estate, net of tax                 96,350 121,923 93,655
Disposal Group, Held-for-sale or Disposed of by Sale, Not Discontinued Operations                      
Disposal Group, Including Discontinued Operation, Income Statement Disclosures                      
Revenues                 32,170 37,062 39,211
Expenses                 (27,415) (32,457) (37,570)
Gain on sale of real estate, net of tax                 132,858 2,197 13,338
Impairment charges                 (29,183) 0 0
Loss on extinguishment of debt                 (15,807) 0 0
Provision for income taxes                 (24) (4) (29)
Income before gain on sale of real estate, net of tax                 $ 92,599 $ 6,798 $ 14,950