Commitments and Contingencies - Narrative (Details)
$ in Millions
6 Months Ended 42 Months Ended
Nov. 25, 2015
USD ($)
Jun. 30, 2018
USD ($)
tenant
claim
Jun. 30, 2018
USD ($)
tenant
claim
Apr. 01, 2016
USD ($)
Sep. 08, 2015
Property
Loss Contingencies [Line Items]          
Outstanding claims | claim   0 0    
Total commitments   $ 57.6 $ 57.6    
Total commitments relating to future acquisitions   21.8 21.8    
Funded commitments   56.0 $ 56.0    
Contingently liable amount of debt owed by tenant   $ 5.7      
Number of tenants indemnified by | tenant   1 1    
Haggen Operations Holdings, LLC Bankruptcy Claim          
Loss Contingencies [Line Items]          
Stipulated claims collected     $ 5.5    
Remaining claims   $ 21.9 $ 21.9    
Haggen Operations Holdings, LLC          
Loss Contingencies [Line Items]          
Bankruptcy claims settled       $ 3.4  
Albertons, LLC          
Loss Contingencies [Line Items]          
Bankruptcy claims settled       $ 3.0  
Spirit Realty, Inc. | Haggen Operations Holdings, LLC          
Loss Contingencies [Line Items]          
Initial litigation settlement $ 21.0        
Subsidiaries | Haggen Operations Holdings, LLC          
Loss Contingencies [Line Items]          
Number of leased properties | Property         20