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Related Party Transactions and Arrangements - Additional Information (Detail)
1 Months Ended 12 Months Ended
Jun. 30, 2017
USD ($)
Property
Dec. 31, 2019
USD ($)
Property
Dec. 31, 2018
USD ($)
Property
Dec. 31, 2017
USD ($)
Related Party Transaction [Line Items]        
Asset management fees earned   $ 7,726,000 $ 6,963,000 $ 6,006,000
Number of property acquired | Property   806 2,379  
Acquisition of real estate properties   $ 128,908,000 $ 215,833,000 221,813,000
Former External Advisor | North Carolina        
Related Party Transaction [Line Items]        
Number of property acquired | Property 328      
Acquisition of real estate properties $ 42,950,000      
Former External Advisor | Management Expenses        
Related Party Transaction [Line Items]        
Asset management fees earned   0 63,000 257,000
Shared Services Agreement | Former External Advisor        
Related Party Transaction [Line Items]        
Cost incurred for service provided   $ 0 $ 0 $ 727,000
Term of agreement   December 21, 2016 to June 20, 2017