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Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)
12 Months Ended
Dec. 31, 2017
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Significant Accounting Policies [Line Items]        
Capitalized cost   $ 0 $ 0 $ 0
Real estate taxes   0 0 $ 0
Impairment of real estate assets   $ 2,608,000    
Sale of real estate description   Real estate sales are recognized when all of the following criteria are met: (1) a sale is consummated, (2) the buyer has demonstrated an adequate commitment to pay for the property, (3) the Company’s receivable is not subject to future subordination, and (4) the Company has transferred the risks and rewards of ownership to the buyer and does not have continuing involvement.    
Lessor operating lease description   A lease arrangement is classified as an operating lease if none of the following criteria are met: (i) ownership transfers to the lessee prior to or shortly after the end of the lease term, (ii) lessee has a bargain purchase option during or at the end of the lease term, (iii) the lease term is greater than or equal to 75% of the underlying property’s estimated useful life, or (iv) the present value of the future minimum lease payments (excluding executory costs) is greater than or equal to 90% of the fair value of the leased property. If one or more of these criteria are met, and the minimum lease payments are determined to be reasonably predictable and collectible, the lease arrangement is generally accounted for as a direct financing lease. Consistent with FASB Accounting Standards Codification (“ASC”) ASC 840, Leases, if the fair value of the land component is 25% or more of the total fair value of the leased property, the land is considered separately from the building for purposes of applying the lease term and minimum lease payments criterion in (iii) and (iv) above    
Lease term as percentage of property's useful life 75.00% 75.00%    
Present value of future minimum lease payments as percentage of fair value of leased property 90.00% 90.00%    
Fair value of land component as percentage of leased property 25.00% 25.00%    
Rents received in advance $ 8,585,000 $ 8,585,000 7,566,000  
Allowance for doubtful notes receivable 0 0    
Tenant reserve 627,000 627,000 480,000  
Tenant and capital reserves 943,000 943,000 $ 767,000  
Obligation to fund capital improvements $ 0 $ 0    
Percentage of economic interests owned by non-controlling interests 7.60% 7.60% 8.60% 10.40%
Fair value of debt $ 1,177,197,000 $ 1,177,197,000 $ 873,026,000  
Carrying amount of debt 1,181,470,000 $ 1,181,470,000 869,524,000  
Percentage of income tax benefit likely of being realized upon settlement   more than 50%    
Uncertain tax positions 0 $ 0 0 $ 0
Revenue from tax reimbursed from tenants   2,877,000 2,004,000 1,994,000
Decrease ( increase) in restricted cash   724,000 (1,381,000) 4,150,000
Accounting Standards Update201515 | Unsecured Revolver        
Significant Accounting Policies [Line Items]        
Debt issuance costs, net 3,431,000 3,431,000 2,386,000  
Accumulated amortization, debt issuance costs 405,000 405,000 1,940,000  
Accounting Standards Update201515 | Mortgage And Notes Payable        
Significant Accounting Policies [Line Items]        
Debt issuance costs, net 1,040,000 1,040,000 1,291,000  
Accumulated amortization, debt issuance costs 402,000 402,000 453,000  
Accounting Standards Update201515 | Unsecured Term Notes        
Significant Accounting Policies [Line Items]        
Debt issuance costs, net 4,788,000 4,788,000 3,641,000  
Accumulated amortization, debt issuance costs 1,700,000 1,700,000 1,532,000  
ASU 2017-01        
Significant Accounting Policies [Line Items]        
Acquisition costs capitalized 12,349,000 12,349,000    
Capital Reserve [Member]        
Significant Accounting Policies [Line Items]        
Tenant and capital reserves $ 316,000 316,000 287,000  
Tenants        
Significant Accounting Policies [Line Items]        
Direct payment for property taxes   19,700,000 16,200,000 12,000,000
Property taxes expense   $ 2,899,000 $ 1,933,000 $ 1,987,000
Minimum        
Significant Accounting Policies [Line Items]        
Capitalization rate   7.25%    
Lease term   9 years    
Minimum | Federal and State Taxing Authorities        
Significant Accounting Policies [Line Items]        
Tax years under examination 2014      
Maximum        
Significant Accounting Policies [Line Items]        
Capitalization rate   12.00%    
Lease term   29 years    
Maximum | Federal and State Taxing Authorities        
Significant Accounting Policies [Line Items]        
Tax years under examination 2017      
Weighted Average        
Significant Accounting Policies [Line Items]        
Discount rate   8.00%    
Broadstone Net Lease, LLC        
Significant Accounting Policies [Line Items]        
Percentage of economic interests owned 92.40% 92.40% 91.40% 89.60%
Percentage of economic interests owned by non-controlling interests 7.60% 7.60% 8.60% 10.40%