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- Real Estate Transactions - Narrative (Details) |  | 3 Months Ended |  |  |
--- | --- | --- | --- | --- | ---
Nov. 05, 2019 USD ($) a shares | Mar. 31, 2021 USD ($) shares | Mar. 31, 2020 USD ($) | Mar. 05, 2021 USD ($) a | Dec. 31, 2020 USD ($) | Jan. 01, 2019 leaseExtensionOption
Real Estate [Line Items] |  |  |  |  |  |
Assets placed in service |  | $ 2,220,504,000 |  |  | $ 2,124,796,000 |
Lease renewal term |  |  |  |  |  | 5 years
Right-of-use asset |  | 701,200 |  |  |  |
Operating lease liability |  | 724,100 |  |  |  |
Deferred leasing costs, net |  | 26,169,000 |  |  | 26,872,000 |
Accumulated amortization deferred leasing cost |  | 45,600,000 |  |  | $ 44,500,000 |
Depreciation expense |  | 11,500,000 | $ 10,000,000.0 |  |  |
Repairs and maintenance expense |  | 3,900,000 | 2,800,000 |  |  |
Impairment of real estate |  | $ 0 |  |  |  |
Number of partnership units issued in transaction (in shares) | shares |  | 1,416,071 |  |  |  |
Business acquisition, expenses reimbursed |  |  |  | $ 7,400,000 |  |
Remaining lease term |  | 61 years |  |  |  |
Operating Lease, annual increase in rent, percentage |  | 1.50% |  |  |  |
Operating lease, incremental borrowing rate |  | 5.63% |  |  |  |
Finance lease, right-of-use asset, amortization |  | $ 26,500 |  |  |  |
Finance lease, interest expense |  | $ 36,800 |  |  |  |
Contribution Agreement |  |  |  |  |  |
Real Estate [Line Items] |  |  |  |  |  |
Right-of-use asset |  |  |  | 19,400,000 |  |
Operating lease liability |  |  |  | 19,400,000 |  |
Number of partnership units issued in transaction (in shares) | shares | 1,416,071 |  |  |  |  |
Asset acquisition consideration transferred | $ 79,300,000 |  |  |  |  |
Business acquisition, transaction costs |  |  |  | $ 1,200,000 |  |
BF Saul Real Estate Investment Trust | Contribution Agreement |  |  |  |  |  |
Real Estate [Line Items] |  |  |  |  |  |
Area of land | a | 10.3 |  |  |  |  |
Minimum |  |  |  |  |  |
Real Estate [Line Items] |  |  |  |  |  |
Operating lease term of contract |  | 1 year |  |  |  |
Maximum |  |  |  |  |  |
Real Estate [Line Items] |  |  |  |  |  |
Operating lease term of contract |  | 15 years |  |  |  |
Building | Minimum |  |  |  |  |  |
Real Estate [Line Items] |  |  |  |  |  |
Estimated useful life |  | 35 years |  |  |  |
Building | Maximum |  |  |  |  |  |
Real Estate [Line Items] |  |  |  |  |  |
Estimated useful life |  | 50 years |  |  |  |
Building Improvements | Maximum |  |  |  |  |  |
Real Estate [Line Items] |  |  |  |  |  |
Estimated useful life |  | 20 years |  |  |  |
Lease Acquisition Costs |  |  |  |  |  |
Real Estate [Line Items] |  |  |  |  |  |
Amortization of intangible assets |  | $ 1,200,000 | $ 1,300,000 |  |  |
The Waycroft and Ashbrook Marketplace |  |  |  |  |  |
Real Estate [Line Items] |  |  |  |  |  |
Assets placed in service |  | $ 8,700,000 |  |  |  |
Corporate Headquarters |  |  |  |  |  |
Real Estate [Line Items] |  |  |  |  |  |
Number of options to extend lease | leaseExtensionOption |  |  |  |  |  | 1
Twinbrook Metro Station | BF Saul Real Estate Investment Trust | Contribution Agreement |  |  |  |  |  |
Real Estate [Line Items] |  |  |  |  |  |
Area of land | a |  |  |  | 6.8 |  |
Twinbrook Metro Station Leasehold Interest | BF Saul Real Estate Investment Trust | Contribution Agreement |  |  |  |  |  |
Real Estate [Line Items] |  |  |  |  |  |
Area of land | a |  |  |  | 1.3 |  |

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- Definition For an unclassified balance sheet, the accumulated amortization, as of the reporting date, which represents the periodic charge to earnings of initial direct costs which have been deferred and are being allocated over the lease term in proportion to the recognition of rental income. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 20 -Section 35 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=121598990&loc=d3e40879-112712 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 20 -Section 25 -Paragraph 16 -URI http://asc.fasb.org/extlink&oid=121585684&loc=d3e40588-112709 + Details
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- Definition This element represents costs incurred by the lessor that are (a) costs to originate a lease incurred in transactions with independent third parties that (i) result directly from and are essential to acquire that lease and (ii) would not have been incurred had that leasing transaction not occurred and (b) certain costs directly related to specified activities performed by the lessor for that lease. Those activities are: evaluating the prospective lessee's financial condition; evaluating and recording guarantees, collateral, and other security arrangements; negotiating lease terms; preparing and processing lease documents; and closing the transaction. This element is net of accumulated amortization. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 20 -Section 25 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=121585684&loc=d3e40246-112709 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 20 -Section 25 -Paragraph 16 -URI http://asc.fasb.org/extlink&oid=121585684&loc=d3e40588-112709 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 20 -Section 35 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=121598990&loc=d3e40879-112712 + Details
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