Annual report pursuant to Section 13 and 15(d)

Organization and Significant Accounting Policies (Details)

v2.4.0.6
Organization and Significant Accounting Policies (Details) (USD $)
 1 Months Ended 12 Months Ended 1 Months Ended 12 Months Ended
Apr. 30, 2005
Dec. 31, 2012
Financial_Institutions
Property
Dec. 31, 2011
Dec. 31, 2010
Apr. 15, 2005
Feb. 29, 2012
Series C Preferred Stock [Member]
Dec. 31, 2012
Series C Preferred Stock [Member]
Dec. 31, 2012
Real Estate [Member]
Dec. 31, 2011
Real Estate [Member]
Dec. 31, 2010
Real Estate [Member]
Dec. 31, 2012
GCLP Business Trust I [Member]
Dec. 31, 2012
GCLP Business Trust II [Member]
Dec. 31, 2012
Gladstone Commercial Advisers, Inc. [Member]
Dec. 31, 2012
Building and building improvements [Member]
Dec. 31, 2012
Maximum [Member]
Dec. 31, 2011
Maximum [Member]
Dec. 31, 2010
Maximum [Member]
Dec. 31, 2012
Maximum [Member]
Equipment and fixtures [Member]
Dec. 31, 2012
Minimum [Member]
Dec. 31, 2011
Minimum [Member]
Dec. 31, 2010
Minimum [Member]
Dec. 31, 2012
Minimum [Member]
Equipment and fixtures [Member]
Organization and Significant Accounting Policies (Textual) [Abstract]                                            
Company ownership percentage of voting securities of Commercial Advisers                         100.00%                  
Percentage of limited partnership interest transferred to business unit                     99.00% 1.00%                    
Number of trust shares exchanged for limited partnership interest                     100                      
Number of trust shares exchanged for general partnership interest                       100                    
Estimated useful life                           39 years       7 years       5 years
Expected lease up period for estimating carrying costs                             18 months       9 months      
Real estate depreciation expense               $ 11,900,000 $ 10,100,000 $ 9,500,000                        
Amortization related to above-market lease                             300,000 300,000 300,000          
Amortization related to below-market lease                                     1,100,000 1,000,000 900,000  
Remaining term of in-place leases and unamortized lease                             15 years       10 years      
Series C preferred stock           7.125% 7.125%                              
Percentage of discount rate for calculating undiscounted obligation                             7.60%       2.50%      
REIT taxable income to its stockholders                             100.00%       90.00%      
Organization and Significant Accounting Policies (Additional Textual) [Abstract]                                            
Total amortization expense related to intangible assets   4,900,000 4,000,000 3,700,000                                    
Number of properties impaired   0                                        
Impairment charges   0                                        
Maturity period of highly-liquid investments at the time of purchase   three months or less                                        
Number of financial institutions   2                                        
Payments of deferred financing costs   4,598,000 1,065,000 1,192,000                                    
Total amortization expense related to deferred financing costs is included in interest expense   1,502,000 918,000 1,003,000                                    
Uncertain tax positions percentage   50.00%                                        
Uncertain tax positions   0 0 0                                    
Liabilities accrued   300,000 100,000 600,000                                    
Recorded expenses   168,000 157,000 143,000                                    
Aggregate undiscounted obligation on properties   9,200,000                                        
Expected payment to be made in next twelve months   0                                        
Expected payment to be made in second year   0                                        
Expected payment to be made in third year   0                                        
Expected payment to be made in fourth year   0                                        
Expected payment to be made in fifth year   0                                        
Originated a mortgage loan         10,000,000                                  
Maturity of mortgage loan May 31, 2017                                          
Mortgage loan fully repaid Jul. 31, 2010                                          
Additional income and prepayment fees $ 3,300,000                                          
Number of properties classified as discontinued operations   0