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Stock-based compensation - Narrative (Details) - USD ($) $ in Thousands |  |  |  | 3 Months Ended | 9 Months Ended | 12 Months Ended |
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Apr. 05, 2022 | Apr. 05, 2019 | Apr. 11, 2012 | Sep. 30, 2025 | Sep. 30, 2024 | Sep. 30, 2025 | Sep. 30, 2024 | Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2012 | May 09, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |
Stock based compensation cost |  |  |  | $ 21,994 | $ 19,516 | $ 63,335 | $ 46,381 |  |  |  |
Options granted, contractual period, years |  |  |  |  |  | 10 years |  |  |  |  |
Options granted (in shares) |  |  |  |  |  | 0 | 0 |  |  |  |
Unrecognized stock-based compensation cost for options |  |  |  | 2,060 |  | $ 2,060 |  |  |  |  |
Restricted stock unit vesting right (in shares) |  |  |  |  |  | 1 |  |  |  |  |
Restricted stock unit vesting right, fair value (in shares) |  |  |  |  |  | 1 |  |  |  |  |
Performance units vesting right (in shares) |  |  |  |  |  | 1 |  |  |  |  |
Employee Stock Option |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |
Weighted average remaining requisite vesting period |  |  |  |  |  | 10 months 24 days |  |  |  |  |
Restricted Stock Units (RSUs) |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |
Weighted average remaining requisite vesting period |  |  |  |  |  | 2 years |  |  |  |  |
Vested, number of shares (in shares) |  |  |  |  |  | 810,027 |  |  |  |  |
Net settlement on vesting of restricted share unit (in shares) |  |  |  |  |  | 502,558 |  |  |  |  |
Unrecognized stock-based compensation cost |  |  |  | 56,833 |  | $ 56,833 |  |  |  |  |
Restricted Stock Units (RSUs) | Vesting Period Two Thousand Twenty Four |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |
Vested, number of shares (in shares) |  |  |  |  |  |  |  | 22,551 |  |  |
Net settlement on vesting of restricted share unit (in shares) |  |  |  |  |  | 13,626 |  |  |  |  |
Restricted Stock Units (RSUs) | Vesting Period Two Thousand Twenty Three |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |
Vested, number of shares (in shares) |  |  |  |  |  |  |  |  | 47,193 |  |
Net settlement on vesting of restricted share unit (in shares) |  |  |  |  |  | 46,982 |  |  |  |  |
Performance Units |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |
Weighted average remaining requisite vesting period |  |  |  |  |  | 1 year 10 months 24 days |  |  |  |  |
Vested, number of shares (in shares) |  |  |  |  |  | 1,154,998 |  |  |  |  |
Unrecognized stock-based compensation cost |  |  |  | $ 62,212 |  | $ 62,212 |  |  |  |  |
Vested, net of withholding tax (in shares) |  |  |  |  |  | 738,490 |  |  |  |  |
Performance Units | Prior to 2023 |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |
Performance units vesting right, fair value (in shares) |  |  |  |  |  | 1 |  |  |  |  |
Performance units period |  |  |  |  |  | 1 year |  |  |  |  |
Performance Units | 2023 |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |
Performance units period |  |  |  |  |  | 3 years |  |  |  |  |
Employee Stock Purchase Plan |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |
Fair value per share allowed to eligible employees to purchase through payroll deductions (in percentage) |  |  |  |  |  | 90.00% |  |  |  |  |
Maximum percentage of employee's base salary allowed to be purchased (in percentage) |  |  |  | 15.00% |  | 15.00% |  |  |  |  |
Maximum dollar amount of common shares allowed to be purchased |  |  |  |  |  | $ 25 |  |  |  |  |
Common shares reserved for issuance (in shares) |  |  |  | 4,200,000 |  | 4,200,000 |  |  |  |  |
Issuance of common shares under the employee stock purchase plan (in shares) |  |  |  |  |  | 178,811 | 261,281 |  |  |  |
Compensation expense for ESPP |  |  |  | $ 227 | $ 210 | $ 720 | $ 895 |  |  |  |
Minimum |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |
Award, vesting period |  |  |  |  |  | 3 years |  |  |  |  |
Minimum | Restricted Stock Units (RSUs) |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |
Award, vesting period |  |  |  |  |  | 3 months |  |  |  |  |
Minimum | Performance Units |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |
Award, vesting period |  |  |  |  |  | 6 months |  |  |  |  |
Maximum |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |
Award, vesting period |  |  |  |  |  | 5 years |  |  |  |  |
Maximum | Restricted Stock Units (RSUs) |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |
Award, vesting period |  |  |  |  |  | 4 years |  |  |  |  |
Maximum | Performance Units |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |
Award, vesting period |  |  |  |  |  | 3 years |  |  |  |  |
2007 Omnibus Plan |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |
Amended omnibus plan, increase in number of common shares authorized for issuance (in shares) | 3,500,000 | 8,000,000 | 5,593,200 |  |  |  |  |  |  | 8,858,823 |
Number of common shares authorized for issuance (in shares) | 26,500,000 | 23,000,000 | 15,000,000 |  |  |  |  |  |  |  |
2017 Omnibus Incentive Compensation Plan |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |
Number of common shares authorized for issuance (in shares) |  |  |  |  |  |  |  |  |  |  | 15,000,000

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