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Real Estate - Additional Information (Detail) |  |  | 12 Months Ended |  |  |
--- | --- | --- | --- | --- | --- | ---
Jun. 29, 2021 USD ($) shares | Mar. 15, 2021 USD ($) | Dec. 31, 2021 USD ($) shares | Dec. 31, 2020 USD ($) | Dec. 31, 2019 USD ($) | Mar. 05, 2021 USD ($) a | Nov. 05, 2019 a | Dec. 31, 2018 USD ($)
Real Estate Properties [Line Items] |  |  |  |  |  |  |  |
Lessee, operating lease, incremental borrowing rate |  |  | 5.63% |  |  |  |  |
Finance lease, right-of-use asset, amortization |  |  | $ 104,000 |  |  |  |  |
Finance lease, interest expense |  |  | 362,800 |  |  |  |  |
Construction in progress |  |  | 205,911,000 | $ 69,477,000 |  |  |  |
Total purchase price |  |  | 2,284,126,000 | 2,124,796,000 | $ 2,081,597,000 |  |  | $ 1,948,165,000
Below market lease, carrying amount |  |  | 23,300,000 | 23,700,000 |  |  |  |
Below market lease, accumulated amortization |  |  | 16,200,000 | 15,000,000 |  |  |  |
Accretion income, intangible liabilities |  |  | 1,400,000 | 1,400,000 | 1,500,000 |  |  |
Lease acquisition costs |  |  |  |  |  |  |  |
Real Estate Properties [Line Items] |  |  |  |  |  |  |  |
Intangible assets gross carrying amount |  |  | 11,000,000 | 11,000,000 |  |  |  |
Intangible assets, accumulated amortization |  |  | 9,100,000 | 8,600,000 |  |  |  |
Amortization expense |  |  | $ 500,000 | 600,000 | 900,000 |  |  |
Weighted-average amortization period |  |  | 4 years 7 months 6 days |  |  |  |  |
Above Market Leases |  |  |  |  |  |  |  |
Real Estate Properties [Line Items] |  |  |  |  |  |  |  |
Intangible assets gross carrying amount |  |  | $ 600,000 | 600,000 |  |  |  |
Intangible assets, accumulated amortization |  |  | 161,800 | 128,900 |  |  |  |
Amortization expense |  |  | $ 32,900 | 43,600 | $ 109,600 |  |  |
Weighted-average amortization period |  |  | 6 years 9 months 18 days |  |  |  |  |
Below Market Leases |  |  |  |  |  |  |  |
Real Estate Properties [Line Items] |  |  |  |  |  |  |  |
Weighted-average amortization period |  |  | 4 years 10 months 24 days |  |  |  |  |
2018 Acquisitions |  |  |  |  |  |  |  |
Real Estate Properties [Line Items] |  |  |  |  |  |  |  |
Total purchase price |  |  |  |  |  |  |  | $ 108,300,000
Contribution Agreement |  |  |  |  |  |  |  |
Real Estate Properties [Line Items] |  |  |  |  |  |  |  |
Business acquisition, transaction costs |  |  |  |  |  | $ 1,200,000 |  |
Right-of-use asset obtained in exchange for finance lease liability |  | $ 19,400,000 |  |  |  |  |  |
Finance lease, liability |  |  |  |  |  | $ 19,400,000 |  |
Contribution Agreement | BF Saul Real Estate Investment Trust |  |  |  |  |  |  |  |
Real Estate Properties [Line Items] |  |  |  |  |  |  |  |
Area of land | a |  |  |  |  |  |  | 10.3 |
Leasehold Interest Contributed In Contribution Agreement |  |  |  |  |  |  |  |
Real Estate Properties [Line Items] |  |  |  |  |  |  |  |
Asset acquisition, consideration transferred | $ 21,500,000 |  |  |  |  |  |  |
Payments to acquire businesses, gross | $ 700,000 |  |  |  |  |  |  |
Leasehold Interest Contributed In Contribution Agreement | Limited Partner |  |  |  |  |  |  |  |
Real Estate Properties [Line Items] |  |  |  |  |  |  |  |
Stock issued during period, shares, acquisitions | shares | 469,740 |  |  |  |  |  |  |
Twinbrook Metro Station |  |  |  |  |  |  |  |
Real Estate Properties [Line Items] |  |  |  |  |  |  |  |
Stock issued during period, shares, acquisitions | shares |  |  | 469,740,000 |  |  |  |  |
Twinbrook Metro Station | Restricted Stock Units (RSUs) |  |  |  |  |  |  |  |
Real Estate Properties [Line Items] |  |  |  |  |  |  |  |
Stock issued during period, shares, acquisitions | shares |  |  | 1,416,071,000 |  |  |  |  |
Twinbrook Metro Station | Contribution Agreement | BF Saul Real Estate Investment Trust |  |  |  |  |  |  |  |
Real Estate Properties [Line Items] |  |  |  |  |  |  |  |
Area of land | a |  |  |  |  |  | 6.8 | 6.8 |
Twinbrook Metro Station Leasehold Interest | Contribution Agreement | BF Saul Real Estate Investment Trust |  |  |  |  |  |  |  |
Real Estate Properties [Line Items] |  |  |  |  |  |  |  |
Area of land | a |  |  |  |  |  | 1.3 | 1.3 |
Twinbrook Quarter |  |  |  |  |  |  |  |
Real Estate Properties [Line Items] |  |  |  |  |  |  |  |
Business acquisition, expenses reimbursed |  |  |  |  |  | $ 7,400,000 |  |
Construction in progress |  |  | $ 138,069,000 | 0 |  |  |  |
7316 Wisconsin Avenue |  |  |  |  |  |  |  |
Real Estate Properties [Line Items] |  |  |  |  |  |  |  |
Construction in progress |  |  | $ 56,898,000 | $ 50,723,000 |  |  |  |

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