v3.8.0.1
Non-Controlling Interests - Additional Information (Detail) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Minority Interest [Line Items]      
Properties contributed as part of UPREIT transactions, value $ 10,498 $ 7,190 $ 57,583
Properties contributed as part of UPREIT transactions, value, net of debt assumed $ 112,949 $ 102,451 $ 95,261
Membership units, issued 1,551 1,427 1,330
Membership units, outstanding 1,551 1,427 1,330
Percentage of economic interests owned by non-controlling interests 7.60% 8.60% 10.40%
Number of membership units exchanged 37,000 0 0
Value of common stock issued upon exchange of membership units $ 0    
Rental income related to UPREIT transactions 13,153 $ 11,843 $ 5,259
Additional Paid-in Capital      
Minority Interest [Line Items]      
Value of common stock issued upon exchange of membership units $ 2,986    
Common Stock      
Minority Interest [Line Items]      
Number of common stock issued upon exchange of membership units 37,000    
Value of common stock issued upon exchange of membership units $ 0