| Share-Based Compensation and Other Compensation Matters (Tables)
 | 12 Months Ended | 
| Dec. 31, 2023 | 
|---|
| Share-Based Payment Arrangement [Abstract] |  | 
| Schedule of Reporting for Share-Based Compensation Expense | The table below sets forth our reporting for share based compensation cost (in thousands): 
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
|  |  | For the Years Ended December 31, |  
|  |  | 2023 |  | 2022 |  | 2021 |  
| General, administrative, leasing and other expenses |  | $ | 7,255 |  |  | $ | 7,643 |  |  | $ | 6,881 |  |  
| Property operating expenses |  | 1,289 |  |  | 1,147 |  |  | 1,098 |  |  
| Capitalized to development activities |  | 576 |  |  | 847 |  |  | 719 |  |  
| Share-based compensation cost |  | $ | 9,120 |  |  | $ | 9,637 |  |  | $ | 8,698 |  |  | 
| Schedule of Restricted Share and TB-PIU Activity | The following table summarizes restricted shares activity under our share-based compensation plan for 2021, 2022 and 2023: 
 The following table summarizes TB-PIUs activity under our share-based compensation plan for 2021, 2022 and 2023:
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
|  |  | Shares |  | Weighted Average Grant Date Fair Value |  
| Unvested as of December 31, 2020 |  | 360,817 |  |  | $ | 26.16 |  |  
| Granted |  | 177,995 |  |  | $ | 26.17 |  |  
| Forfeited |  | (39,664) |  |  | $ | 26.62 |  |  
| Vested |  | (164,575) |  |  | $ | 25.95 |  |  
| Unvested as of December 31, 2021 |  | 334,573 |  |  | $ | 26.22 |  |  
| Granted |  | 186,515 |  |  | $ | 26.50 |  |  
| Forfeited |  | (43,420) |  |  | $ | 26.47 |  |  
| Vested |  | (152,585) |  |  | $ | 26.39 |  |  
| Unvested as of December 31, 2022 |  | 325,083 |  |  | $ | 26.27 |  |  
| Granted |  | 220,336 |  |  | $ | 25.38 |  |  
| Forfeited |  | (39,474) |  |  | $ | 26.03 |  |  
| Vested |  | (152,490) |  |  | $ | 26.09 |  |  
| Unvested as of December 31, 2023 |  | 353,455 |  |  | $ | 25.82 |  |  
| Unvested shares as of December 31, 2023 that are expected to vest |  | 317,075 |  |  | $ | 25.83 |  |  
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
|  |  | Number of TB-PIUs |  | Weighted Average Grant Date Fair Value |  
| Unvested as of December 31, 2020 |  | 114,334 |  |  | $ | 25.57 |  |  
| Granted |  | 93,983 |  |  | $ | 26.16 |  |  
|  |  |  |  |  |  
| Vested |  | (45,244) |  |  | $ | 25.28 |  |  
| Unvested as of December 31, 2021 |  | 163,073 |  |  | $ | 25.99 |  |  
| Granted |  | 101,966 |  |  | $ | 26.39 |  |  
|  |  |  |  |  |  
| Vested |  | (77,709) |  |  | $ | 26.04 |  |  
| Unvested as of December 31, 2022 |  | 187,330 |  |  | $ | 26.19 |  |  
| Granted |  | 123,900 |  |  | $ | 25.40 |  |  
| Forfeited |  | (27,182) |  |  | $ | 26.46 |  |  
| Vested |  | (89,633) |  |  | $ | 25.95 |  |  
| Unvested as of December 31, 2023 |  | 194,415 |  |  | $ | 25.76 |  |  
| Unvested TB-PIUs as of December 31, 2023 that are expected to vest |  | 193,131 |  |  | $ | 25.76 |  |  | 
| Schedule of PB-PIU's Granted | 
We made the following grants of PB-PIUs to senior management team members from 2019 through 2023 (dollars in thousands, except per share data):
 
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
| Grant Date |  | Number of PB-PIUs Granted |  |  |  |  |  | Grant Date Fair Value |  | Number of PB-PIUs Outstanding as of December 31, 2023 |  
| 1/1/2019 |  | 193,682 |  |  |  |  |  |  | $ | 2,415 |  |  | — |  |  
| 1/1/2020 |  | 176,758 |  |  |  |  |  |  | $ | 2,891 |  |  | — |  |  
| 1/1/2021 |  | 227,544 |  |  |  |  |  |  | $ | 3,417 |  |  | 189,308 |  |  
| 1/1/2022 |  | 231,838 |  |  |  |  |  |  | $ | 3,810 |  |  | 192,996 |  |  
| 1/1/2023 |  | 275,402 |  |  |  |  |  |  | $ | 4,343 |  |  | 225,590 |  |  | 
| Schedule of Payouts for Defined Performance Under PB-PIU | The number of earned awards at the end of the performance period will be determined based on the percentile rank of COPT Defense’s total shareholder return (“TSR”) relative to a peer group of companies, as set forth in the following schedule: 
|  |  |  |  |  |  |  |  |  |  
| Percentile Rank |  | Earned Awards Payout % |  
| 75th or greater |  | 100% of PB-PIUs granted |  
| 50th (target) |  | 50% of PB-PIUs granted |  
| 25th |  | 25% of PB-PIUs granted |  
| Below 25th |  | 0% of PB-PIUs granted |  | 
| Schedule of Assumptions Used in Monte Carlo Models for PB-PIUs | The grant date fair value and certain of the assumptions used in the Monte Carlo models for the PB-PIUs granted in 2021, 2022 and 2023 are set forth below: 
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
| Grant Date |  | Grant Date Fair Value Per PB-PIU at Target-Level Award |  | Baseline Common Share Value |  | Expected Volatility of Common Shares |  | Risk-free Interest Rate |  
| 1/1/2021 |  | $ | 30.03 |  |  | $ | 26.08 |  |  | 34.7 | % |  | 0.18 | % |  
| 1/1/2022 |  | $ | 32.87 |  |  | $ | 27.97 |  |  | 31.7 | % |  | 0.98 | % |  
| 1/1/2023 |  | $ | 31.54 |  |  | $ | 25.94 |  |  | 35.0 | % |  | 4.28 | % |  | 
| Schedule of Deferred Shares Granted | We made the following grants of deferred share awards to non-employee Trustees in 2021, 2022 and 2023 (dollars in thousands, except per share data): 
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
| Year of Grant |  | Number of Deferred Share Awards Granted |  | Aggregate Grant Date Fair Value |  | Grant Date Fair Value Per Award |  
| 2021 |  | 3,416 |  |  | $ | 93 |  |  | $ | 27.12 |  |  
| 2022 |  | 6,771 |  |  | $ | 166 |  |  | $ | 24.50 |  |  
| 2023 |  | 9,046 |  |  | $ | 215 |  |  | $ | 23.75 |  |  |