| Cover | 12 Months Ended |
| Dec. 31, 2022 | |
| Document Information [Line Items] | |
| Document Type | DEF 14A |
| Amendment Flag | false |
| Entity Information [Line Items] | |
| Entity Registrant Name | FRANKLIN STREET PROPERTIES CORP. |
| Entity Central Index Key | 0001031316 |
| Pay vs Performance Disclosure | 12 Months Ended | ||
| Dec. 31, 2022 USD ($) | Dec. 31, 2021 USD ($) | Dec. 31, 2020 USD ($) | |
| Pay vs Performance Disclosure [Table] | |||
| Pay vs Performance [Table Text Block] | PAY VERSUS PERFORMANCE The following table reports the compensation of our Principal Executive Officer (PEO) and the average compensation of the other Named Executive Officers (Other NEOs) as reported in the Summary Compensation Table for the past three fiscal years, as well as their “compensation actually paid” as calculated pursuant to the SEC’s pay versus performance rules and certain performance measures required by such rules. Value of Initial Fixed $100 Year (1) Summary PEO Compensation Average Average FSP’s Total Peer Group (2) Net Income Debt (3) 2022 $ 306,000 $ 306,000 $ 674,773 $ 674,773 $ 40.20 $ 62.07 $ 1,094,000 $ 152,000,000 2021 $ 806,000 $ 806,000 $ 753,326 $ 753,326 $ 84.25 $ 99.51 $ 92,717,000 $ 540,000,000 2020 $ 306,000 $ 306,000 $ 724,708 $ 724,708 $ 54.63 $ 81.56 $ 32,615,000 $ 151,500,000 (1) For all years, Mr. George J. Carter served as our PEO and Mr. John G. Demeritt, Mr. Jeffrey B. Carter, Mr. Scott H. Carter and Mr. John F. Donahue served as the Other NEOs. (2) For all years, the peer group is the FTSE NAREIT Equity Office Index. (3) While our Compensation Committee employs a subjective approach to the consideration of various measures of corporate performance, for 2022, the Company identified the amount of debt repaid as the most important financial performance measure used to link the compensation actually paid to the PEO and the Other NEOs for 2022 to the Company’s performance. The amount of debt repaid is calculated from the Company’s Consolidated Statements of Cash Flows by adding “Repayment of term loans payable” to “Repayments of bank note payable”. (4) The following table lists the seven most important financial performance measures used by the Company to link compensation actually paid to the PEO and the Other NEOs in 2022 to the Company’s performance: Debt repaid Gross proceeds from property dispositions Amount (and terms) of space leased Funds from operations (FFO) Dividends paid Total stockholder return Estimated net asset value (5) In the “Compensation Discussion and Analysis” section of this Proxy Statement, we provide greater detail on the elements of our executive compensation program and our compensation philosophy. We believe the Company’s executive compensation program and the executive compensation decisions included in the 2022 Summary Compensation Table and related disclosures appropriately reward our PEO and the Other NEOs for Company and individual performance, assist the Company in retaining our senior leadership team and support long-term value creation for our stockholders. | ||
| Company Selected Measure Name | Debt Repaid | ||
| Named Executive Officers, Footnote [Text Block] | (1) For all years, Mr. George J. Carter served as our PEO and Mr. John G. Demeritt, Mr. Jeffrey B. Carter, Mr. Scott H. Carter and Mr. John F. Donahue served as the Other NEOs. | ||
| Peer Group Issuers, Footnote [Text Block] | (2) For all years, the peer group is the FTSE NAREIT Equity Office Index. | ||
| PEO Total Compensation Amount | $ 306,000 | $ 806,000 | $ 306,000 |
| PEO Actually Paid Compensation Amount | 306,000 | 806,000 | 306,000 |
| Non-PEO NEO Average Total Compensation Amount | 674,773 | 753,326 | 724,708 |
| Non-PEO NEO Average Compensation Actually Paid Amount | $ 674,773 | 753,326 | 724,708 |
| Compensation Actually Paid vs. Total Shareholder Return [Text Block] | |||
| Compensation Actually Paid vs. Net Income [Text Block] | |||
| Tabular List [Table Text Block] | (4) The following table lists the seven most important financial performance measures used by the Company to link compensation actually paid to the PEO and the Other NEOs in 2022 to the Company’s performance: Debt repaid Gross proceeds from property dispositions Amount (and terms) of space leased Funds from operations (FFO) Dividends paid Total stockholder return Estimated net asset value | ||
| Total Shareholder Return Amount | $ 40.2 | 84.25 | 54.63 |
| Peer Group Total Shareholder Return Amount | 62.07 | 99.51 | 81.56 |
| Net Income (Loss) | $ 1,094,000 | $ 92,717,000 | $ 32,615,000 |
| Company Selected Measure Amount | 152,000,000 | 540,000,000 | 151,500,000 |
| PEO Name | Mr. George J. Carter | ||
| Measure [Axis]: 1 | |||
| Pay vs Performance Disclosure [Table] | |||
| Measure Name | Debt repaid | ||
| Non-GAAP Measure Description [Text Block] | (3) While our Compensation Committee employs a subjective approach to the consideration of various measures of corporate performance, for 2022, the Company identified the amount of debt repaid as the most important financial performance measure used to link the compensation actually paid to the PEO and the Other NEOs for 2022 to the Company’s performance. The amount of debt repaid is calculated from the Company’s Consolidated Statements of Cash Flows by adding “Repayment of term loans payable” to “Repayments of bank note payable”. | ||
| Measure [Axis]: 2 | |||
| Pay vs Performance Disclosure [Table] | |||
| Measure Name | Gross proceeds from property dispositions | ||
| Measure [Axis]: 3 | |||
| Pay vs Performance Disclosure [Table] | |||
| Measure Name | Amount (and terms) of space leased | ||
| Measure [Axis]: 4 | |||
| Pay vs Performance Disclosure [Table] | |||
| Measure Name | Funds from operations (FFO) | ||
| Measure [Axis]: 5 | |||
| Pay vs Performance Disclosure [Table] | |||
| Measure Name | Dividends paid | ||
| Measure [Axis]: 6 | |||
| Pay vs Performance Disclosure [Table] | |||
| Measure Name | Total stockholder return | ||
| Measure [Axis]: 7 | |||
| Pay vs Performance Disclosure [Table] | |||
| Measure Name | Estimated net asset value | ||
