Quarterly report pursuant to Section 13 or 15(d)

RELATED PARTY TRANSACTIONS (Details)

v3.19.3
RELATED PARTY TRANSACTIONS (Details)
$ in Thousands
3 Months Ended 9 Months Ended
Jun. 01, 2019
USD ($)
shares
Sep. 30, 2019
USD ($)
Sep. 30, 2018
USD ($)
Sep. 30, 2019
USD ($)
property
Sep. 30, 2018
USD ($)
Related Party Transaction [Line Items]          
Payroll and related costs reimbursed to the PROs by the Company   $ 28,988 $ 26,552 $ 82,635 $ 76,962
Ownership interest in reinsurance company acquired (percent) 5.50%        
Equity interest in reinsurance company $ 500        
Supervisory and Administrative Fee Agreement | Management | Participating Regional Operator (PRO)          
Related Party Transaction [Line Items]          
Supervisory and administrative fees paid to the PROs   5,200 4,400 $ 14,800 12,600
Supervisory and Administrative Fee Agreement | Management | Participating Regional Operator (PRO) | Minimum          
Related Party Transaction [Line Items]          
Supervisory and administrative fee agreement of gross revenue, percent       5.00%  
Supervisory and Administrative Fee Agreement | Management | Participating Regional Operator (PRO) | Maximum          
Related Party Transaction [Line Items]          
Supervisory and administrative fee agreement of gross revenue, percent       6.00%  
Payroll Services | Management | Participating Regional Operator (PRO)          
Related Party Transaction [Line Items]          
Payroll and related costs reimbursed to the PROs by the Company   8,100 7,400 $ 23,800 21,900
Due Diligence Costs | Management | Participating Regional Operator (PRO)          
Related Party Transaction [Line Items]          
Due diligence expenses payable to the PROs   $ 100 $ 100 $ 700 $ 300
Real Estate Purchases | Corporate Joint Venture          
Related Party Transaction [Line Items]          
Number of properties acquired | property       1  
Consideration in acquisition transaction       $ 4,100  
Acquisition of Interest in Reinsurance Company | Ground Up          
Related Party Transaction [Line Items]          
Consideration in acquisition transaction 15,100        
Cash paid in acquisition 6,600        
Acquisition of Interest in Reinsurance Company | Management          
Related Party Transaction [Line Items]          
Cash paid in acquisition 2,200        
Tenant reinsurance intangible          
Related Party Transaction [Line Items]          
Recognized fair value allocated to intangible assets $ 14,600        
Weighted average remaining useful life (in years) 25 years        
OP units | NSA OP, LP | Acquisition of Interest in Reinsurance Company | Ground Up          
Related Party Transaction [Line Items]          
OP units issued in acquisition (in shares) | shares 285,512        
Value of OP units issued in acquisition $ 8,500        
OP units | NSA OP, LP | Acquisition of Interest in Reinsurance Company | Management          
Related Party Transaction [Line Items]          
OP units issued in acquisition (in shares) | shares 95,170        
Value of OP units issued in acquisition $ 2,800