Commitments and Contingencies - Narrative (Details)
$ in Millions
9 Months Ended
Nov. 25, 2015
USD ($)
Sep. 30, 2017
USD ($)
Property
tenant
claim
location
Apr. 01, 2016
USD ($)
Sep. 08, 2015
Property
Loss Contingencies [Line Items]        
Number of properties sold | Property   7    
Proceeds from sale of locations | $   $ 58.3    
Number of leases sold which were previously rejected | location   5    
Number of locations owned with in-place leases | location   11    
Number of vacant locations | location   2    
Outstanding claims | claim   0    
Total commitments | $   $ 54.1    
Total commitments relating to future acquisitions | $   11.3    
Funded commitments | $   33.0    
Contingently liable amount of debt owed by tenant | $   $ 5.7    
Number of tenants indemnified by | tenant   1    
Haggen Operations Holdings, LLC Bankruptcy Claim        
Loss Contingencies [Line Items]        
Stipulated claims collected | $   $ 5.5    
Haggen Operations Holdings, LLC        
Loss Contingencies [Line Items]        
Bankruptcy claims settled | $     $ 3.4  
Locations returned upon settlement | location   7    
Number of lease location affirmed under bankruptcy | location   13    
Albertons, LLC        
Loss Contingencies [Line Items]        
Bankruptcy claims for rent reduction settled | $     $ 3.0  
Spirit Realty, Inc. | Haggen Operations Holdings, LLC        
Loss Contingencies [Line Items]        
Initial litigation settlement | $ $ 21.0      
Haggen Operations Holdings, LLC        
Loss Contingencies [Line Items]        
Number of leased properties | Property       20
Albertson's LLC | Haggen Operations Holdings, LLC        
Loss Contingencies [Line Items]        
Number of lease location affirmed under bankruptcy | location   5    
Smart and Final LLC | Haggen Operations Holdings, LLC        
Loss Contingencies [Line Items]        
Number of lease location affirmed under bankruptcy | location   5    
Gleason's Markets | Haggen Operations Holdings, LLC        
Loss Contingencies [Line Items]        
Number of lease location affirmed under bankruptcy | location   2    
Safeway | Haggen Operations Holdings, LLC        
Loss Contingencies [Line Items]        
Number of lease location affirmed under bankruptcy | location   1