Quarterly report pursuant to Section 13 or 15(d)

Organization, Basis of Presentation and Significant Accounting Policies - Additional Information (Detail)

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Organization, Basis of Presentation and Significant Accounting Policies - Additional Information (Detail) (USD $)
 3 Months Ended 9 Months Ended
Sep. 30, 2014
Sep. 30, 2013
Sep. 30, 2014
Subsidiary
Sep. 30, 2013
Organization And Significant Accounting Policies [Line Items]        
Number of subsidiaries interest owned in general and limited partnership     2  
Non-qualifying income related to real estate portfolio     $ 0  
Adjusted net income due to error correction 300,000   0  
Amortization related to below-market lease 200,000 200,000 500,000 400,000
Total amortization expense related to intangible assets 2,600,000 2,000,000 7,200,000 5,200,000
Payments of deferred financing costs 100,000 1,300,000 711,000 1,484,000
Total amortization expense related to deferred financing costs included in interest expense 400,000 600,000 1,209,000 1,410,000
Liabilities accrued     200,000 0
Expenses recorded to general and administrative expense 40,000 30,000 100,000 100,000
Aggregate undiscounted obligation on properties 9,500,000   9,500,000  
Expected payment to be made in next twelve months 0   0  
Expected payment to be made in second year 0   0  
Expected payment to be made in third year 0   0  
Expected payment to be made in fourth year 0   0  
Expected payment to be made in fifth year 0   0  
Real Estate [Member]
        
Organization And Significant Accounting Policies [Line Items]        
Real estate depreciation expense 4,800,000 4,200,000 13,800,000 11,200,000
Minimum [Member]
        
Organization And Significant Accounting Policies [Line Items]        
Expected lease up period for estimating carrying costs     9 months  
Remaining term of in-place leases and unamortized lease     10 years  
Percentage of discount rate for calculating undiscounted obligation     2.50%  
Maximum [Member]
        
Organization And Significant Accounting Policies [Line Items]        
Expected lease up period for estimating carrying costs     18 months  
Remaining term of in-place leases and unamortized lease     15 years  
Percentage of discount rate for calculating undiscounted obligation     7.60%  
Above Market Leases [Member]
        
Organization And Significant Accounting Policies [Line Items]        
Amortization related to above-market lease $ 100,000 $ 100,000 $ 200,000 $ 200,000
Building and Improvements [Member]
        
Organization And Significant Accounting Policies [Line Items]        
Estimated useful life     39 years  
Equipment and Fixtures [Member] | Minimum [Member]
        
Organization And Significant Accounting Policies [Line Items]        
Estimated useful life     5 years  
Equipment and Fixtures [Member] | Maximum [Member]
        
Organization And Significant Accounting Policies [Line Items]        
Estimated useful life     20 years  
Gladstone Commercial Advisers, Inc. [Member]
        
Organization And Significant Accounting Policies [Line Items]        
Company ownership percentage of voting securities of Commercial Advisers     100.00%  
GCLP Business Trust I [Member]
        
Organization And Significant Accounting Policies [Line Items]        
Percentage of limited partnership interest transferred to business unit     99.00%  
Number of trust shares exchanged for limited partnership interest     100  
Subsidiary and business trust of the Company, formed under the laws of the Commonwealth of Massachusetts, date     Dec. 28, 2005  
GCLP Business Trust II [Member]
        
Organization And Significant Accounting Policies [Line Items]        
Percentage of limited partnership interest transferred to business unit     1.00%  
Number of trust shares exchanged for general partnership interest     100  
Subsidiary and business trust of the Company, formed under the laws of the Commonwealth of Massachusetts, date     Dec. 28, 2005