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Share-based compensation - Additional Information (Details) - USD ($) |  | 1 Months Ended | 12 Months Ended
--- | --- | --- | ---
Mar. 01, 2014 | Jun. 30, 2019 | Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Share-based compensation |  |  |  |  |  |
Income tax benefit |  |  | $ 1,400,000 | $ 1,000,000.0 | $ 1,400,000 |
Long-term incentive plan (LTIP) |  |  |  |  |  |
Share-based compensation |  |  |  |  |  |
Performance period |  |  | 3 years |  |  |
Exception to forfeiture, minimum requisite service period |  |  | 12 months |  |  |
Payout low end of range |  |  | 0.00% |  |  |
Payout high end of range |  |  | 200.00% |  |  |
Restricted stock units |  |  |  |  |  |
Share-based compensation |  |  |  |  |  |
Fair value |  |  | $ 3,000,000 | 4,200,000 | 3,200,000 |
Income tax benefit |  |  | 600,000 | 700,000 | 500,000 |
Unrecognized compensation cost |  |  | $ 4,600,000 |  |  |
Weighted-average period over which unrecognized compensation cost expected to be recognized |  |  | 2 years |  |  |
LTIP linked to TRS |  |  |  |  |  |
Share-based compensation |  |  |  |  |  |
Fair value |  |  | $ 800,000 | 2,600,000 |  |
Income tax benefit |  |  | 200,000 | 400,000 |  |
Unrecognized compensation cost |  |  | $ 1,000,000 |  |  |
Weighted-average period over which unrecognized compensation cost expected to be recognized |  |  | 1 year 7 months 6 days |  |  |
LTIP awards linked to other performance conditions |  |  |  |  |  |
Share-based compensation |  |  |  |  |  |
Fair value |  |  | $ 1,700,000 | 7,600,000 | $ 0 |
Income tax benefit |  |  | 400,000 | $ 1,200,000 |  |
Unrecognized compensation cost |  |  | $ 3,400,000 |  |  |
Weighted-average period over which unrecognized compensation cost expected to be recognized |  |  | 1 year 8 months 12 days |  |  |
Equity and Incentive Plan (EIP) |  |  |  |  |  |
Share-based compensation |  |  |  |  |  |
Additional shares available for issuance (in shares) | 1,500,000 |  |  |  |  |
Shares remaining available for future issuance (in shares) |  |  | 2,900,000 |  |  |
Shares that can be issued upon vesting of outstanding units and achievement of performance goals (in shares) |  |  | 500,000 |  |  |
Equity and Incentive Plan (EIP) | Restricted shares |  |  |  |  |  |
Share-based compensation |  |  |  |  |  |
Vesting period |  |  | 3 years | 4 years | 4 years | 4 years
Equity and Incentive Plan (EIP) | Restricted shares | Share-based Payment Arrangement, Tranche One |  |  |  |  |  |
Share-based compensation |  |  |  |  |  |
Vesting percentage |  |  | 33.33% | 25.00% | 25.00% | 25.00%
Equity and Incentive Plan (EIP) | Restricted shares | Share-based Payment Arrangement, Tranche Two |  |  |  |  |  |
Share-based compensation |  |  |  |  |  |
Vesting percentage |  |  | 33.33% | 25.00% | 25.00% | 25.00%
Equity and Incentive Plan (EIP) | Restricted shares | Share-based Payment Arrangement, Tranche Three |  |  |  |  |  |
Share-based compensation |  |  |  |  |  |
Vesting percentage |  |  | 33.33% | 25.00% | 25.00% | 25.00%
Equity and Incentive Plan (EIP) | Restricted shares | Share-Based Payment Arrangement, Tranche Four |  |  |  |  |  |
Share-based compensation |  |  |  |  |  |
Vesting percentage |  |  |  | 25.00% | 25.00% | 25.00%
Nonemployee Director Stock Plan |  |  |  |  |  |
Share-based compensation |  |  |  |  |  |
Additional shares available for issuance (in shares) |  | 300,000 |  |  |  |
Shares remaining available for future issuance (in shares) |  |  | 244,347 |  |  |

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- Definition Represents the requisite minimum months of service in the performance period required in order to qualify for the forfeiture exception in the event of death, disability and retirement, on completion of requisite minimum months of service. + References No definition available. + Details
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- Definition Represents the high end of range of payout depending on achievement of the goals. + References No definition available. + Details
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- Definition Represents the number of shares that could be issued upon vesting of share-based payment awards and achievement of performance goals. + References No definition available. + Details
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- Definition Represents the number of authorized but unissued shares that could be issued under the equity-based compensation plan. + References No definition available. + Details
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- Definition Amount of cost not yet recognized for nonvested award under share-based payment arrangement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition Amount of tax benefit for recognition of expense of award under share-based payment arrangement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(1)(i) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d)(2) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Definition Number of additional shares authorized for issuance under share-based payment arrangement. + References No definition available. + Details
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- Definition The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition Percentage of vesting of award under share-based payment arrangement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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