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Share-based compensation plans - Additional Information (Details) $ / shares in Units, $ in Thousands | 12 Months Ended | 48 Months Ended
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Dec. 31, 2023 USD ($) installment $ / shares shares | Dec. 31, 2022 USD ($) $ / shares shares | Dec. 31, 2021 USD ($) $ / shares shares | Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Shares available for grant (in shares) | shares | 5,069,768 |  |  |
Compensation cost for share-based payment arrangements | $ 27,780 | $ 31,309 | $ 22,608 |
Related tax benefit recognized in net income | 6,920 | 7,999 | 5,715 |
Additional net excess tax benefit realized | $ 978 | $ 1,367 | $ 1,110 |
Restricted Stock Units (RSUs) |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Granted, weighted-average grant date fair value (usd per share) | $ / shares | $ 56.87 |  |  |
Vested units in period (in shares) | shares | 0 |  |  |
Performance Contingent Restricted Stock Units (PCSUs) |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Minimum vesting period | 3 years |  |  |
Granted, weighted-average grant date fair value (usd per share) | $ / shares | $ 55.04 | $ 51.94 | $ 55.95 |
Noncash stock-based compensation associated performance contingent restricted stock units | $ 10,751 | $ 17,900 | $ 11,477 |
Total unrecognized compensation cost related to nonvested awards | $ 8,746 |  |  |
Weighted-average period | 16 months |  |  |
Performance period | 3 years |  |  |
Stock return payout percentage | 0.20 |  |  |
Number of common shares to be converted into for each share upon conversion | 1 |  |  |
Vested units in period (in shares) | shares | 0 |  |  |
Performance Contingent Restricted Stock Units (PCSUs) | 2023 PCSU |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Performance period | 3 years |  |  |
Total performance contingent restricted stock units vested , minimum (in shares) | shares | 0 |  |  |
Total performance contingent restricted stock units, maximum (in shares) | shares | 449,255 |  |  |
Performance Contingent Restricted Stock Units (PCSUs) | 2022 PCSU |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Performance period | 3 years |  |  |
Total performance contingent restricted stock units vested , minimum (in shares) | shares | 0 |  |  |
Total performance contingent restricted stock units, maximum (in shares) | shares | 342,808 |  |  |
Performance Contingent Restricted Stock Units (PCSUs) | 2021 PCSU |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Fair value of vested units | $ 12,600 |  |  |
Total performance contingent restricted stock units, maximum (in shares) | shares | 225,530 |  |  |
Performance Contingent Restricted Stock Units (PCSUs) | 2020 PCSU |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Fair value of vested units |  | $ 17,052 |  |
Vested units in period (in shares) | shares |  | 280,881 |  |
Performance Contingent Restricted Stock Units (PCSUs) | 2019 PCSU |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Fair value of vested units |  |  | $ 3,719 |
Vested units in period (in shares) | shares |  |  | 64,243 |
Performance Contingent Restricted Stock Units (PCSUs) | Minimum |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Vesting percentage | 25.00% |  |  |
Performance Contingent Restricted Stock Units (PCSUs) | Maximum |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Vesting percentage | 75.00% |  |  |
Stock Appreciation Rights (SARs) |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Compensation cost for share-based payment arrangements | $ 0 | $ 40 | $ 347 |
Total unrecognized compensation cost related to nonvested awards | $ 0 |  |  |
Vesting percentage | 33.33% |  |  |
Aggregate intrinsic value of options and SARs exercised | $ 158 | 582 | 2,575 |
Weighted average remaining contractual life for SAR's, outstanding | 4 years 1 month 6 days |  |  |
Aggregate intrinsic value for SAR's, outstanding | $ 2,217 |  |  |
Fair market value of the Company’s stock used to calculate intrinsic value (usd per share) | $ / shares | $ 55.87 |  |  |
Stock Appreciation Rights (SARs) | Granted 2015 through 2019 |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Minimum vesting period |  |  |  | 3 years
Term of award | 10 years |  |  |
Deferred Compensation Plans |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Compensation deferrals in current year | $ 2,024 | $ 2,256 | $ 2,507 |
Executive Officers and Key Management Employees | Restricted Stock Units (RSUs) |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Minimum vesting period | 3 years |  |  |
Executive Officers and Key Management Employees | Restricted Stock Units (RSUs) | Share-based Compensation Award, Tranche One |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Vesting percentage | 33.33% |  |  |
Executive Officers and Key Management Employees | Restricted Stock Units (RSUs) | Share-based Compensation Award, Tranche Two |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Vesting percentage | 33.33% |  |  |
Executive Officers and Key Management Employees | Restricted Stock Units (RSUs) | Share-based Compensation Award, Tranche Three |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Vesting percentage | 33.33% |  |  |
Executives and Directors | Restricted Stock Units (RSUs) |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Minimum vesting period | 5 years |  |  |
Granted, weighted-average grant date fair value (usd per share) | $ / shares | $ 56.87 | $ 53.55 | $ 57.77 |
Fair value of vested units | $ 10,320 | $ 6,243 | $ 4,063 |
Noncash stock-based compensation associated performance contingent restricted stock units | 15,005 | $ 11,113 | $ 8,278 |
Total unrecognized compensation cost related to nonvested awards | $ 11,674 |  |  |
Weighted-average period | 26 months |  |  |
Executives and Directors | Restricted Stock Units (RSUs) | Share-based Compensation Award, Tranche Three |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Vesting percentage | 33.33% |  |  |
Executives and Directors | Restricted Stock Units (RSUs) | Share-based Compensation Award, Tranche Four |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Vesting percentage | 33.33% |  |  |
Executives and Directors | Restricted Stock Units (RSUs) | Share-based Compensation Award, Tranche Five |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Vesting percentage | 33.33% |  |  |
Non-employee directors | Deferred Compensation Plans | Share-based Compensation Award, Tranche One |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Number of annual distribution installments | installment | 1 |  |  |
Non-employee directors | Deferred Compensation Plans | Share-based Compensation Award, Tranche Two |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Number of annual distribution installments | installment | 3 |  |  |
Non-employee directors | Deferred Compensation Plans | Share-based Compensation Award, Tranche Three |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Number of annual distribution installments | installment | 5 |  |  |

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- Definition Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 718 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (d)(2) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480429/718-10-50-2 + Details
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- Definition Percentage of vesting of award under share-based payment arrangement. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 718 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (a)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480429/718-10-50-2 + Details
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