| Fiscal period | 2025 | 2024 | 2023 | 2022 | 2021 | 2020 | 2019 | 2018 | 2017 | 2016 |
| Period End Date | 12/31/2025 | 12/31/2024 | 12/31/2023 | 12/31/2022 | 12/31/2021 | 12/31/2020 | 12/31/2019 | 12/31/2018 | 12/31/2017 | 12/31/2016 |
| Consulting | 88.19 | 97.25 | 118.23 | 152.59 | 156.11 | 144.36 | -- | -- | -- | -- |
| Research services | 295.61 | 316.74 | 334.40 | 354.45 | 325.34 | 294.49 | 298.74 | 228.40 | 216.47 | 215.22 |
| Advisory services and other | -- | -- | -- | -- | -- | -- | 162.96 | 129.18 | 121.20 | 110.88 |
| Events | 13.09 | 18.48 | 28.16 | 30.75 | 12.86 | 10.14 | -- | -- | -- | -- |
| Total Revenues | 396.89 | 432.47 | 480.78 | 537.79 | 494.32 | 448.98 | 461.70 | 357.58 | 337.67 | 326.10 |
| Cost of services and fulfillment | 170.72 | 182.53 | 204.48 | 223.77 | 201.82 | 180.90 | 196.73 | 146.50 | 136.87 | 128.18 |
| Gross Profit | -- | -- | 276.30 | 314.01 | 292.50 | 268.09 | 264.97 | 211.07 | 200.80 | 197.92 |
| Depreciation | 6.03 | 7.56 | 8.45 | 9.27 | 9.39 | 9.88 | 8.57 | 7.96 | 6.65 | 7.81 |
| Goodwill impairment | 110.71 | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| Amortization of intangible assets | 8.75 | 9.65 | 11.96 | 13.16 | 15.13 | 19.68 | 22.62 | 1.16 | 0.78 | 0.83 |
| General and Administrative | 52.66 | 58.82 | 68.50 | 67.66 | 58.06 | 50.37 | 53.04 | 43.92 | 41.91 | 40.58 |
| Selling and marketing | 149.48 | 159.62 | 167.35 | 181.94 | 170.95 | 166.20 | 172.87 | 131.82 | 123.92 | 116.90 |
| Reorganization costs | 11.72 | 11.77 | 13.27 | 9.34 | -- | -- | -- | -- | -- | 1.03 |
| Integration costs | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| Acquisition and integration costs | -- | -- | -- | -- | (0.33) | (5.78) | (8.95) | (3.79) | -- | -- |
| Loss from sale of divested operation | -- | (1.78) | -- | -- | -- | -- | -- | -- | -- | -- |
| Total Operating Expenses | 510.06 | 431.73 | 474.01 | 505.13 | 455.67 | 432.81 | 462.77 | 335.15 | 310.12 | 295.32 |
| Operating Income (loss) | (113.17) | 0.74 | 6.77 | 32.65 | 38.64 | 16.18 | (1.08) | 22.43 | 27.55 | 30.77 |
| Interest expense | 2.68 | 3.01 | 3.06 | 2.46 | 4.22 | 5.34 | 8.05 | -- | -- | -- |
| Gains on sales of available-for-sale securities | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| Gains from non-marketable investments, net of impairments | -- | 0.81 | -- | -- | -- | -- | -- | -- | -- | -- |
| Gains (losses) on investments, net | 0.00 | -- | 0.21 | 0.31 | -- | 2.47 | 0.05 | 0.43 | (0.48) | (0.81) |
| Other income (loss) net | 3.75 | 4.09 | 2.37 | 0.22 | (1.23) | (0.37) | (0.52) | 0.67 | 0.30 | 0.74 |
| Credit loss expense | (7.31) | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| Income from Continuing Operations Before Income Tax Provision | (119.41) | 2.64 | 6.29 | 30.72 | 33.19 | 12.93 | (9.60) | 23.53 | 27.37 | 30.71 |
| Income tax (benefit) provision | (0.05) | 8.38 | 3.24 | 8.92 | 8.35 | 2.94 | (0.03) | 8.15 | 12.23 | 13.06 |
| Current-Federal | -- | -- | 3.87 | 9.35 | 4.20 | 0.60 | 0.62 | 2.28 | 2.59 | 6.09 |
| Current-State | -- | -- | 1.92 | 3.82 | 2.27 | 2.05 | 0.91 | 1.17 | 1.06 | 2.33 |
| Deferred-Federal | -- | -- | (3.87) | (5.51) | 0.33 | 0.49 | (1.45) | 2.11 | 5.55 | 2.72 |
| Deferred-State | -- | -- | (1.60) | (1.79) | (0.66) | (1.64) | (2.01) | 0.67 | 0.70 | 0.06 |
| Current-Foreign | -- | -- | 2.91 | 2.40 | 2.15 | 1.96 | 2.40 | 1.76 | 2.16 | 2.03 |
| Deferred-Foreign | -- | -- | 0.01 | 0.65 | 0.05 | (0.53) | (0.50) | 0.15 | 0.18 | (0.18) |
| Less-valuation allowance | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| Income from Continuing Operations | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| Gain (loss) on sale of discontinued operations, net of taxes | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| Income (loss) from discontinued operations, net of taxes | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| Net Income (Loss) Available to Common Shareholders | (119.36) | (5.75) | 3.05 | 21.81 | 24.84 | 9.99 | (9.57) | 15.38 | 15.14 | 17.65 |
| Basic income per common share from continuing operations | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| Basic income (loss) per common share from discontinued operations | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| Net Earnings Per Share (Basic) | (6.28) | (0.30) | 0.16 | 1.15 | 1.30 | 0.53 | (0.52) | 0.85 | 0.84 | 0.98 |
| Diluted income per common share from continuing operations | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| Diluted (loss) income per common share from discontinued operations | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| Net Earnings Per Share (Diluted) | (6.28) | (0.30) | 0.16 | 1.14 | 1.28 | 0.53 | (0.52) | 0.84 | 0.83 | 0.97 |
| Weighted Average Shares Outstanding (Basic) | 19.02 | 19.09 | 19.18 | 18.97 | 19.11 | 18.83 | 18.49 | 18.09 | 17.92 | 17.98 |
| Weighted Average Shares Outstanding (Diluted) | 19.02 | 19.09 | 19.26 | 19.17 | 19.36 | 18.94 | 18.49 | 18.38 | 18.24 | 18.27 |