| Line Item | Jun 30, 2026 | Mar 31, 2026 | Dec 31, 2025 | Sep 30, 2025 | Jun 30, 2025 | Mar 31, 2025 | Dec 31, 2024 | Sep 30, 2024 | Jun 30, 2024 | Mar 31, 2024 | Dec 31, 2023 | Sep 30, 2023 | Jun 30, 2023 | Mar 31, 2023 | Dec 31, 2022 | Sep 30, 2022 |
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| Revenues | ||||||||||||||||
| Expenses | ||||||||||||||||
| Compensation and benefits | ||||||||||||||||
| Occupancy | ||||||||||||||||
| Professional fees | ||||||||||||||||
| Communication, technology and information services | ||||||||||||||||
| Travel and related expenses | ||||||||||||||||
| Depreciation and amortization | ||||||||||||||||
| Other expenses | ||||||||||||||||
| Total expenses | ||||||||||||||||
| Operating income (loss) | ||||||||||||||||
| Other income and (expenses) | ||||||||||||||||
| Income (loss) before income taxes | ||||||||||||||||
| Provision (benefit) for income taxes | ||||||||||||||||
| Net income (loss) | ||||||||||||||||
| Net income (loss) attributable to noncontrolling interests | ||||||||||||||||
| Net income (loss) attributable to Moelis & Company | ||||||||||||||||
| Net income (loss) per share attributable to holders of shares of Class A common stock | ||||||||||||||||
| Basic (in dollars per share) | ||||||||||||||||
| Diluted (in dollars per share) |