v3.8.0.1
Acquisitions - Acquisitions Closed (Parenthetical) - (Detail) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Business Acquisition [Line Items]      
Mortgages assumed $ 11,926 $ 0 $ 0
ASU 2017-01      
Business Acquisition [Line Items]      
Acquisition costs capitalized 12,349    
Healthcare      
Business Acquisition [Line Items]      
Mortgages assumed $ 5,205    
Interest rate 1-month LIBOR plus 3.0%    
Mortgage, Maturity date Aug. 31, 2021    
Healthcare | LIBOR      
Business Acquisition [Line Items]      
Mortgage, Interest rate 3.00%    
Healthcare | Interest Rate Swap      
Business Acquisition [Line Items]      
Derivative, Fixed rate 1.02%    
Derivative, Maturity date Aug. 31, 2021    
Other      
Business Acquisition [Line Items]      
Mortgages assumed $ 6,721    
Mortgage, Interest rate 3.65%    
Mortgage, Maturity date Oct. 31, 2026