XML 146 R130.htm IDEA: XBRL DOCUMENT v3.8.0.1
Subsequent Events (Narrative) (Details)
1 Months Ended 2 Months Ended 3 Months Ended 12 Months Ended
Feb. 29, 2016
center
Feb. 28, 2018
USD ($)
center
Mar. 31, 2017
USD ($)
Dec. 31, 2017
USD ($)
property
Dec. 31, 2016
USD ($)
Dec. 31, 2015
USD ($)
Subsequent Event [Line Items]            
Number of centers sold 1     18    
Impairment loss     $ 15,000,000 $ 15,257,000 $ 98,000 $ 153,000
Subsequent Event [Member]            
Subsequent Event [Line Items]            
Number of centers sold | center   5        
Sales of real estate   $ 220,600,000        
Impairment loss   $ 0