Annual report pursuant to Section 13 and 15(d)

RELATED PARTY TRANSACTIONS - Narrative (Details)

v3.19.3.a.u2
RELATED PARTY TRANSACTIONS - Narrative (Details)
$ in Thousands
 3 Months Ended 12 Months Ended
Jun. 01, 2019
USD ($)
shares
Dec. 31, 2019
USD ($)
property
Sep. 30, 2019
USD ($)
property
Jun. 30, 2019
USD ($)
property
Mar. 31, 2019
USD ($)
property
Dec. 31, 2018
USD ($)
property
Sep. 30, 2018
USD ($)
property
Jun. 30, 2018
USD ($)
property
Mar. 31, 2018
USD ($)
property
Dec. 31, 2019
USD ($)
property
shares
Dec. 31, 2018
USD ($)
property
shares
Dec. 31, 2017
USD ($)
Dec. 31, 2014
USD ($)
property
Related Party Transaction [Line Items]                          
Payroll and related costs reimbursed to the PROs by the Company                   $ 110,347 $ 103,875 $ 84,455  
Number of properties acquired | property   7 6 24 32 7 13 12 25 69 57    
Asset acquisition consideration   $ 32,163 $ 35,771 $ 185,335 $ 194,561 $ 51,395 $ 106,528 $ 62,937 $ 135,789 $ 447,830 $ 356,649    
Ownership interest in reinsurance company acquired (percent) 5.50%                        
Management | Participating Regional Operator (PRO)                          
Related Party Transaction [Line Items]                          
Number of properties acquired | property                         16
Reimbursement for difference between fair value and contractual value of mortgages assumed                         $ 5,200
Reimbursements received for interest payments                   1,300 1,200    
Reimbursements received for principal payments                   $ 1,300 $ 1,200    
Shares or units issued upon reimbursement of assumed mortgages (in units) | shares                   37,770 44,502    
Joint Venture | Asset acquired from 2016 Joint Venture                          
Related Party Transaction [Line Items]                          
Number of properties acquired | property                   1      
Asset acquisition consideration                   $ 4,100      
Supervisory and administrative fee agreement | Management | Participating Regional Operator (PRO)                          
Related Party Transaction [Line Items]                          
Supervisory and administrative fees paid to the PROs                   $ 20,000 $ 16,900 14,400  
Supervisory and administrative fee agreement | Management | Participating Regional Operator (PRO) | Minimum                          
Related Party Transaction [Line Items]                          
Supervisory and administrative fee arrangement 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 arrangement 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                   $ 32,000 29,500 24,600  
Due diligence costs | Management | Participating Regional Operator (PRO)                          
Related Party Transaction [Line Items]                          
Due diligence expenses payable to the PROs                   700 $ 400 $ 700  
Issuance of units to affiliate of Personal Mini | Affiliated entity                          
Related Party Transaction [Line Items]                          
Value of co-investment in acquisition                   $ 400      
Issuance of units to affiliate of Personal Mini | Affiliated entity | Subordinated performance units                          
Related Party Transaction [Line Items]                          
Issuance of shares/units (in shares) | shares                   11,100      
Acquisition of interest in reinsurance company                          
Related Party Transaction [Line Items]                          
Equity interest in reinsurance company $ 500                        
Acquisition of interest in reinsurance company | 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                        
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 | Ground Up | OP units                          
Related Party Transaction [Line Items]                          
OP units issued in acquisition (in shares) | shares 285,512                        
Value of OP units issued in acquisition $ 8,500                        
Acquisition of interest in reinsurance company | Management | OP units                          
Related Party Transaction [Line Items]                          
Cash paid in acquisition $ 2,200                        
OP units issued in acquisition (in shares) | shares 95,170                        
Value of OP units issued in acquisition $ 2,800