| Pay vs Performance Disclosure item in Thousands | 12 Months Ended |
| Dec. 31, 2022 USD ($) item | Dec. 31, 2021 USD ($) item | Dec. 31, 2020 USD ($) item |
| Pay vs Performance Disclosure [Table] | | | |
| Pay vs Performance [Table Text Block] | Value of Initial Fixed $100 Investment Based On: Year Summary Compensation Table Total for PEO (1) ($) Compensation Actually Paid to PEO (2) ($) Average Summary Compensation Table Total for Non-PEO NEOs (3) ($) Average Compensation Actually Paid to Non-PEO NEOs (4) ($) Total Stockholder Return (5) ($) Peer Group Total Stockholder Return (6) ($) Net Loss (7) ($ thousands) Company Selected Measure: NOI (8) ($ thousands) 2022 9,325,413 8,046,688 2,997,166 2,201,029 48 61 (36,403) 397,088 2021 9,746,050 6,593,381 3,462,015 2,980,168 65 97 (20,354) 383,788 2020 9,297,893 3,942,462 2,484,614 1,131,946 68 80 (24,704) 404,727 (1) Reflects the compensation amounts reported in the SCT for our PEO, Mr. Behler , for each of the respective years shown. (2) CAP to our PEO is computed in accordance with SEC rules. The dollar amounts do not reflect the actual amount of compensation earned or paid during the applicable year. In accordance with SEC rules, reconciliation of the adjustments made from SCT total compensation to CAP for Mr. Behler is set forth following the footnotes to this table. (3) For 2022, Other NEOs are Messrs. Paes, Brindley, and Johnson; for 2021 and 2020, Other NEOs are Messrs. Paes, Brindley, Johnson and Mr. David Zobel, former Executive Vice President, Head of Acquisitions. (4) Average CAP to our Other NEOs is computed in accordance with SEC rules. The dollar amounts do not reflect the actual amount of compensation earned or paid during the applicable year. In accordance with SEC rules, reconciliation of the adjustments made from SCT total compensation to CAP for the average of the Other NEOs is set forth following the footnotes to this table. (5) Represents the cumulative TSR of the Company for an initial investment of $100 on December 31, 2019 through and including the end of the fiscal year for each row in the table. (6) Represents the cumulative TSR of the MSCI US REIT/Office REIT Index, which is an industry index reported in the performance graph included in the Company’s 2022 Annual Report on Form 10-K, for an initial investment of $100 on December 31, 2019 through and including the end of the fiscal year for each row in the table. (7) The Company’s Net Income as reported in the Company’s Consolidated Statements of Income on Form 10-K for each fiscal year in the table. (8) The Company’s NOI , which is the Company-Selected Measure, and a non-GAAP measure discussed in our Form 10-K filing. | | |
| Company Selected Measure Name | NOI | | |
| Named Executive Officers, Footnote [Text Block] | (1) Reflects the compensation amounts reported in the SCT for our PEO, Mr. Behler , for each of the respective years shown. (3) For 2022, Other NEOs are Messrs. Paes, Brindley, and Johnson; for 2021 and 2020, Other NEOs are Messrs. Paes, Brindley, Johnson and Mr. David Zobel, former Executive Vice President, Head of Acquisitions. | | |
| Peer Group Issuers, Footnote [Text Block] | (6) Represents the cumulative TSR of the MSCI US REIT/Office REIT Index, which is an industry index reported in the performance graph included in the Company’s 2022 Annual Report on Form 10-K, for an initial investment of $100 on December 31, 2019 through and including the end of the fiscal year for each row in the table. | | |
| PEO Total Compensation Amount | $ 9,325,413 | $ 9,746,050 | $ 9,297,893 |
| PEO Actually Paid Compensation Amount | $ 8,046,688 | 6,593,381 | 3,942,462 |
| Adjustment To PEO Compensation, Footnote [Text Block] | (2) CAP to our PEO is computed in accordance with SEC rules. The dollar amounts do not reflect the actual amount of compensation earned or paid during the applicable year. In accordance with SEC rules, reconciliation of the adjustments made from SCT total compensation to CAP for Mr. Behler is set forth following the footnotes to this table. Reconciliation of SCT Total Compensation to CAP 2022 2021 2020 Average Average Average Other Other Other Non-PEO Non-PEO Non-PEO PEO NEOs PEO NEOs PEO NEOs ($) ($) ($) ($) ($) ($) Summary Compensation Table Total 9,325,413 2,997,166 9,746,050 3,462,015 9,297,893 2,484,614 Add (Subtract): Stock award and option value reported in SCT for the covered year (6,250,000) (1,569,167) (6,250,000) (2,041,875) (6,524,028) (1,401,453) Year-end fair value of equity awards granted during fiscal year that are outstanding and unvested at year-end 5,714,133 1,301,013 5,985,523 1,987,166 3,864,110 818,366 Year-over-Year change in fair value of awards granted in any prior fiscal year that are outstanding and unvested at year-end (881,161) (656,817) (1,195,684) (248,814) (2,080,515) (664,014) Change in fair value from prior year-end to vesting date of awards granted in any prior year that vested during the fiscal year (62,571) 18,256 (1,867,338) (252,966) (869,466) (177,521) Value of dividends or other earnings paid on unvested LTIP units not otherwise reflected in fair value or total compensation 200,874 110,578 174,830 74,642 254,468 71,954 Compensation Actually Paid 8,046,688 2,201,029 6,593,381 2,980,168 3,942,462 1,131,946 The dollar amounts reported represent CAP, as computed in accordance with SEC rules. The fair values of stock option and AOLTIP awards were determined using a Black-Scholes option-pricing model with assumptions applicable to each valuation date. The fair values of performance-based LTIP awards were determined using a Monte Carlo simulation analysis. The fair value of time-based LTIP awards were based on the Company’s closing stock price on each valuation date. The dollar amounts do not reflect the actual amount of compensation earned by or paid during the applicable year. | | |
| Non-PEO NEO Average Total Compensation Amount | $ 2,997,166 | 3,462,015 | 2,484,614 |
| Non-PEO NEO Average Compensation Actually Paid Amount | $ 2,201,029 | 2,980,168 | 1,131,946 |
| Adjustment to Non-PEO NEO Compensation Footnote [Text Block] | (4) Average CAP to our Other NEOs is computed in accordance with SEC rules. The dollar amounts do not reflect the actual amount of compensation earned or paid during the applicable year. In accordance with SEC rules, reconciliation of the adjustments made from SCT total compensation to CAP for the average of the Other NEOs is set forth following the footnotes to this table. Reconciliation of SCT Total Compensation to CAP 2022 2021 2020 Average Average Average Other Other Other Non-PEO Non-PEO Non-PEO PEO NEOs PEO NEOs PEO NEOs ($) ($) ($) ($) ($) ($) Summary Compensation Table Total 9,325,413 2,997,166 9,746,050 3,462,015 9,297,893 2,484,614 Add (Subtract): Stock award and option value reported in SCT for the covered year (6,250,000) (1,569,167) (6,250,000) (2,041,875) (6,524,028) (1,401,453) Year-end fair value of equity awards granted during fiscal year that are outstanding and unvested at year-end 5,714,133 1,301,013 5,985,523 1,987,166 3,864,110 818,366 Year-over-Year change in fair value of awards granted in any prior fiscal year that are outstanding and unvested at year-end (881,161) (656,817) (1,195,684) (248,814) (2,080,515) (664,014) Change in fair value from prior year-end to vesting date of awards granted in any prior year that vested during the fiscal year (62,571) 18,256 (1,867,338) (252,966) (869,466) (177,521) Value of dividends or other earnings paid on unvested LTIP units not otherwise reflected in fair value or total compensation 200,874 110,578 174,830 74,642 254,468 71,954 Compensation Actually Paid 8,046,688 2,201,029 6,593,381 2,980,168 3,942,462 1,131,946 The dollar amounts reported represent CAP, as computed in accordance with SEC rules. The fair values of stock option and AOLTIP awards were determined using a Black-Scholes option-pricing model with assumptions applicable to each valuation date. The fair values of performance-based LTIP awards were determined using a Monte Carlo simulation analysis. The fair value of time-based LTIP awards were based on the Company’s closing stock price on each valuation date. The dollar amounts do not reflect the actual amount of compensation earned by or paid during the applicable year. | | |
| Compensation Actually Paid vs. Total Shareholder Return [Text Block] | Relationship between Company CAP and TSR The graphs below illustrate the relationship between CAP and our TSR for the PEO (top) and Average Other NEOs (bottom) for each of the past three fiscal years. SCT total compensation is also shown for reference. | | |
| Compensation Actually Paid vs. Net Income [Text Block] | Relationship between CAP, Net Income, and NOI The graph below illustrates the relationship between the CAP values for the PEO and Average Other NEOs and our Net Income (Loss) and NOI. Net Income (Loss) is not used as a metric in our annual or long-term incentive plans, and NOI is used in our long-term incentive plan. | | |
| Compensation Actually Paid vs. Company Selected Measure [Text Block] | Relationship between CAP, Net Income, and NOI The graph below illustrates the relationship between the CAP values for the PEO and Average Other NEOs and our Net Income (Loss) and NOI. Net Income (Loss) is not used as a metric in our annual or long-term incentive plans, and NOI is used in our long-term incentive plan. | | |
| Total Shareholder Return Vs Peer Group [Text Block] | Relationship between the Company’s TSR and Peer Group TSR The graph below illustrates the relationship between our three-year cumulative TSR and that of the MSCI US REIT/Office REIT Index, which is the “Peer Group” used in the pay-versus-performance table above. | | |
| Tabular List [Table Text Block] | Tabular List of Performance Measures The following is a list of performance measures, which in our assessment represent the most important performance measures used by the Company to link compensation actually paid to the NEOs for 2022. Each metric below is used for purposes of determining payouts under either our annual incentive program or vesting of our performance stock units. Please see the CD&A for a further description of these metrics and how they are used in the Company’s executive compensation program. ● NOI ● Relative TSR ● Core FFO Per Share ● Square Footage of Signed Leases ● Same Store Leased Occupancy ● Corporate Overhead (general and administrative expenses) ● Fundraising (value of capital raised through funds and joint ventures) NOI is the primary performance metric used to determine payout of LTIP units awarded under our 2022 Performance Program. See page 62 for the description of the 2022 Performance Program. | | |
| Total Shareholder Return Amount | $ 48 | 65 | 68 |
| Peer Group Total Shareholder Return Amount | 61 | 97 | 80 |
| Net Income (Loss) | $ (36,403,000) | $ (20,354,000) | $ (24,704,000) |
| Company Selected Measure Amount | item | 397,088 | 383,788 | 404,727 |
| PEO Name | Mr. Behler | | |
| Measure [Axis]: 1 | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Measure Name | NOI | | |
| Non-GAAP Measure Description [Text Block] | (8) The Company’s NOI , which is the Company-Selected Measure, and a non-GAAP measure discussed in our Form 10-K filing. | | |
| Measure [Axis]: 2 | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Measure Name | Relative TSR | | |
| Measure [Axis]: 3 | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Measure Name | Core FFO Per Share | | |
| Measure [Axis]: 4 | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Measure Name | Square Footage of Signed Leases | | |
| Measure [Axis]: 5 | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Measure Name | Same Store Leased Occupancy | | |
| Measure [Axis]: 6 | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Measure Name | Corporate Overhead (general and administrative expenses) | | |
| Measure [Axis]: 7 | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Measure Name | Fundraising (value of capital raised through funds and joint ventures) | | |
| PEO [Member] | Stock award and option value reported in SCT for the covered year | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | $ (6,250,000) | $ (6,250,000) | $ (6,524,028) |
| PEO [Member] | Year-end fair value of equity awards granted during fiscal year that are outstanding and unvested at year-end | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | 5,714,133 | 5,985,523 | 3,864,110 |
| PEO [Member] | Year-over-Year change in fair value of awards granted in any prior fiscal year that are outstanding and unvested at year-end | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | (881,161) | (1,195,684) | (2,080,515) |
| PEO [Member] | Change in fair value from prior year-end to vesting date of awards granted in any prior year that vested during the fiscal year | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | (62,571) | (1,867,338) | (869,466) |
| PEO [Member] | Value of dividends or other earnings paid on unvested LTIP units not otherwise reflected in fair value or total compensation | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | 200,874 | 174,830 | 254,468 |
| Non-PEO NEO [Member] | Stock award and option value reported in SCT for the covered year | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | (1,569,167) | (2,041,875) | (1,401,453) |
| Non-PEO NEO [Member] | Year-end fair value of equity awards granted during fiscal year that are outstanding and unvested at year-end | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | 1,301,013 | 1,987,166 | 818,366 |
| Non-PEO NEO [Member] | Year-over-Year change in fair value of awards granted in any prior fiscal year that are outstanding and unvested at year-end | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | (656,817) | (248,814) | (664,014) |
| Non-PEO NEO [Member] | Change in fair value from prior year-end to vesting date of awards granted in any prior year that vested during the fiscal year | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | 18,256 | (252,966) | (177,521) |
| Non-PEO NEO [Member] | Value of dividends or other earnings paid on unvested LTIP units not otherwise reflected in fair value or total compensation | | | |
| Pay vs Performance Disclosure [Table] | | | |
| Adjustment to Compensation Amount | $ 110,578 | $ 74,642 | $ 71,954 |
