Variable interest entities ("VIEs") - Schedule of Unfunded Commitments VIEs (Details) - USD ($) $ in Thousands |
Jun. 30, 2026 |
Dec. 31, 2025 |
|---|---|---|
| Variable Interest Entity [Line Items] | ||
| Maximum loss exposure | $ 3,412 | $ 3,234 |
| Location, Statement of Financial Position, Balance [Axis]: us-gaap:Assets | ||
| Variable Interest Entity [Line Items] | ||
| Maximum loss exposure | 3,412 | 3,234 |
| Location, Statement of Financial Position, Balance [Axis]: us-gaap:Liabilities | ||
| Variable Interest Entity [Line Items] | ||
| Maximum loss exposure | 0 | 0 |
| Location, Statement of Financial Position, Balance [Axis]: opy:UnfundedLoanCommitments | ||
| Variable Interest Entity [Line Items] | ||
| Maximum loss exposure | $ 0 | $ 0 |