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Stock-based compensation - Narrative (Detail) - USD ($) |  |  |  |  |  |  |  |  |  |  |  |  |  | 12 Months Ended |
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Dec. 22, 2021 | Sep. 24, 2021 | Jun. 23, 2021 | Mar. 19, 2021 | Dec. 23, 2020 | Sep. 23, 2020 | Jun. 26, 2020 | Mar. 18, 2020 | Dec. 18, 2019 | Sep. 20, 2019 | Jun. 21, 2019 | Apr. 05, 2019 | Mar. 20, 2019 | Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019 | May 09, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stock based compensation cost |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 80,548,000 | $ 72,709,000 | $ 82,802,000 |
Tax benefits recognized in relation to stock-based compensation |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 21,857,000 | $ 21,832,000 | 18,921,000 |
Options granted, contractual period, years |  |  |  |  |  |  |  |  |  |  |  |  |  | 10 years |  |  |
Dividends paid per share (in usd per share) | $ 0.1075 | $ 0.1075 | $ 0.1075 | $ 0.1075 | $ 0.0975 | $ 0.0975 | $ 0.0975 | $ 0.0975 | $ 0.085 | $ 0.085 | $ 0.085 |  | $ 0.085 | $ 0.1075 | $ 0.0975 |  |
Cash received from the exercise of stock option |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 23,168,000 | $ 14,062,000 | 10,690,000 |
Tax benefits from the exercise of stock option |  |  |  |  |  |  |  |  |  |  |  |  |  | 6,927,000 | 7,381,000 | 2,966,000 |
Unrecognized stock-based compensation cost for options |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 24,199,000 |  |  |
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 |  |  |
Performance Units vesting right, fair value (in shares) |  |  |  |  |  |  |  |  |  |  |  |  |  | 1 |  |  |
Employee Stock Option |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Excess tax benefit on stock-based compensation |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 4,191,000 | $ 7,310,000 | $ 2,743,000 |
Weighted average remaining requisite vesting period |  |  |  |  |  |  |  |  |  |  |  |  |  | 3 years 2 months 12 days |  |  |
Restricted Share Units (RSUs) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Weighted average remaining requisite vesting period |  |  |  |  |  |  |  |  |  |  |  |  |  | 2 years 3 months 18 days |  |  |
Unrecognized stock-based compensation cost |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 18,045,000 |  |  |
Performance Units |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Weighted average remaining requisite vesting period |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1 year 9 months 18 days |
Unrecognized stock-based compensation cost |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 58,752,000 |
Employee Stock Purchase Plan |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of fair value per share allowed to eligible employees to purchase through payroll deductions |  |  |  |  |  |  |  |  |  |  |  |  |  | 90.00% |  |  |
Maximum percentage of employee's base salary allowed to be purchased |  |  |  |  |  |  |  |  |  |  |  |  |  | 15.00% |  |  |
Maximum dollar amount of common shares allowed to be purchased |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 25,000 |  |  |
Common shares reserved for issuance |  |  |  |  |  |  |  |  |  |  |  |  |  | 4,200,000 |  |  |
Issuance of common shares under the employee stock purchase plan (Note 18) (in shares) |  |  |  |  |  |  |  |  |  |  |  |  |  | 285,657 | 315,245 | 264,440 |
Compensation expense for ESPP |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 1,420,000 | $ 1,299,000 | $ 1,083,000 |
Minimum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Award, vesting period, years |  |  |  |  |  |  |  |  |  |  |  |  |  | 3 years |  |  |
Minimum | Restricted Share Units (RSUs) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Award, vesting period, years |  |  |  |  |  |  |  |  |  |  |  |  |  | 3 months |  |  |
Minimum | Performance Units |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Award, vesting period, years |  |  |  |  |  |  |  |  |  |  |  |  |  | 6 months |  |  |
Maximum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Award, vesting period, years |  |  |  |  |  |  |  |  |  |  |  |  |  | 5 years |  |  |
Maximum | Restricted Share Units (RSUs) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Award, vesting period, years |  |  |  |  |  |  |  |  |  |  |  |  |  | 4 years |  |  |
Maximum | Performance Units |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Award, vesting period, years |  |  |  |  |  |  |  |  |  |  |  |  |  | 3 years |  |  |
2007 Omnibus Plan |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of common shares authorized for issuance |  |  |  |  |  |  |  |  |  |  |  | 23,000,000 |  | 23,858,823 |  |  |
Amended Omnibus Plan, increase in number of common shares authorized for issuance |  |  |  |  |  |  |  |  |  |  |  | 8,000,000 |  |  |  |  |
2017 Omnibus Incentive Compensation Plan |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of common shares authorized for issuance |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 15,000,000

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