Investments - Narrative (Details)
$ in Thousands
3 Months Ended 9 Months Ended
Sep. 30, 2020
USD ($)
State
Property
Jun. 30, 2020
USD ($)
Mar. 31, 2020
USD ($)
Sep. 30, 2019
USD ($)
Sep. 30, 2020
USD ($)
State
Property
Sep. 30, 2019
USD ($)
Dec. 31, 2019
Property
Real Estate Properties [Line Items]              
Gross investment in owned real estate properties $ 6,400,000       $ 6,400,000    
Portfolio disbursement, number of states | State 48       48    
Minimum of investment in real estate properties 10.00%       10.00%    
Number of properties under operating leases | Property 1,765       1,765   1,745
Number of properties under direct financing lease | Property 1       1    
Sales-type and direct financing leases minimum future payments to be received $ 3,700       $ 3,700    
Direct financing leases, reserve 152   $ 300 $ 0 (152) $ 0  
Direct financing leases, net investment balance 7,600       7,600    
Remaining reserve against net investment 100       100    
Allowance (reversal) for credit losses $ (83) $ (200) $ 300 $ 0 $ 0 $ 0  
Texas              
Real Estate Properties [Line Items]              
Investment in real estate properties 11.50%       11.50%