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Organization, Basis of Presentation and Significant Accounting Policies - Additional Information (Detail) (USD $)
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3 Months Ended | 9 Months Ended | 1 Months Ended | 9 Months Ended | 3 Months Ended | 9 Months Ended | 3 Months Ended | 9 Months Ended | 3 Months Ended | 9 Months Ended | ||||||||||||||
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Sep. 30, 2013
Property
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Sep. 30, 2012
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Sep. 30, 2013
Subsidiary
Property
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Sep. 30, 2012
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Feb. 29, 2012
Series C Preferred Stock [Member]
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Sep. 30, 2013
Series C Preferred Stock [Member]
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Sep. 30, 2013
Minimum [Member]
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Sep. 30, 2012
Minimum [Member]
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Sep. 30, 2013
Minimum [Member]
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Sep. 30, 2012
Minimum [Member]
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Sep. 30, 2013
Maximum [Member]
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Sep. 30, 2012
Maximum [Member]
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Sep. 30, 2013
Maximum [Member]
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Sep. 30, 2012
Maximum [Member]
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Sep. 30, 2013
Real Estate [Member]
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Sep. 30, 2012
Real Estate [Member]
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Sep. 30, 2013
Real Estate [Member]
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Sep. 30, 2012
Real Estate [Member]
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Sep. 30, 2013
Building and Building Improvements [Member]
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Sep. 30, 2013
Equipment and Fixtures [Member]
Minimum [Member]
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Sep. 30, 2013
Equipment and Fixtures [Member]
Maximum [Member]
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Sep. 30, 2013
Gladstone Commercial Advisers, Inc. [Member]
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Sep. 30, 2013
GCLP Business Trust I [Member]
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Sep. 30, 2013
GCLP Business Trust II [Member]
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| Organization And Significant Accounting Policies [Line Items] | ||||||||||||||||||||||||
| Number of subsidiaries interest owned in general and limited partnership | 2 | |||||||||||||||||||||||
| Company ownership percentage of voting securities of Commercial Advisers | 100.00% | |||||||||||||||||||||||
| Non-qualifying income related to real estate portfolio | $ 0 | |||||||||||||||||||||||
| 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 | |||||||||||||||||||||||
| Subsidiary and business trust of the Company, formed under the laws of the Commonwealth of Massachusetts, date | Dec. 28, 2005 | Dec. 28, 2005 | ||||||||||||||||||||||
| Estimated useful life | 39 years | 5 years | 7 years | |||||||||||||||||||||
| Expected lease up period for estimating carrying costs | 9 months | 18 months | ||||||||||||||||||||||
| Real estate depreciation expense | 4,200,000 | 3,000,000 | 11,200,000 | 8,700,000 | ||||||||||||||||||||
| Amortization related to above-market lease | 100,000 | 100,000 | 200,000 | 300,000 | ||||||||||||||||||||
| Amortization related to below-market lease | 200,000 | 300,000 | 400,000 | 800,000 | ||||||||||||||||||||
| Remaining term of in-place leases and unamortized lease | 10 years | 15 years | ||||||||||||||||||||||
| Total amortization expense related to intangible assets | 2,000,000 | 1,200,000 | 5,200,000 | 3,500,000 | ||||||||||||||||||||
| Number of properties impaired | 0 | 0 | ||||||||||||||||||||||
| Expiration period of property lease | 2015-01 | |||||||||||||||||||||||
| Extended period of lease on property | 1 year | |||||||||||||||||||||||
| Impairment charges | 0 | |||||||||||||||||||||||
| Payments of deferred financing costs | 1,300,000 | 500,000 | 1,484,000 | 3,483,000 | ||||||||||||||||||||
| Series C Preferred Stock | 7.125% | 7.125% | ||||||||||||||||||||||
| Total amortization expense related to deferred financing costs is included in interest expense | 600,000 | 400,000 | 1,410,000 | 1,103,000 | ||||||||||||||||||||
| Liabilities accrued | 0 | 300,000 | ||||||||||||||||||||||
| Recorded expenses | 30,000 | 40,000 | 96,000 | 124,000 | ||||||||||||||||||||
| Aggregate undiscounted obligation on properties | 9,200,000 | 9,200,000 | ||||||||||||||||||||||
| Percentage of discount rate for calculating undiscounted obligation | 2.50% | 7.60% | ||||||||||||||||||||||
| 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 | ||||||||||||||||||||||
| Reclassification effect on previously reported net income | $ 0 | $ 0 | $ 0 | $ 0 | ||||||||||||||||||||