Stock-based compensation - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost related to nonvested awards	$ 10,282	$ 10,214	$ 7,089
Dividends declared not paid on restricted stock units	400	238	149
Proceeds from employee payroll withholdings	1,190	919	764
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of restricted stock units vested and released	16,340	5,619	9,923
Compensation cost related to nonvested awards	8,907	9,213	7,089
Unrecognized compensation cost related to nonvested awards	$ 11,652
Expected weighted-average period to be recognized	2 years 6 months
Dividends declared not paid on restricted stock units	$ 274	613
RSUs \| Directors
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost related to nonvested awards	$ 635	898	$ 724
RSUs \| 2016-LTIP Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for issuable (in shares)	1,812,577
PSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost related to nonvested awards	$ 1,375	$ 1,001
Unrecognized compensation cost related to nonvested awards	$ 6,914
Expected weighted-average period to be recognized	1 year 9 months 18 days
Criteria period		3 years
Core return threshold percentages	200.00%
Award vesting, percentage	85.00%	150.00%
PSUs \| Executives and Other Officers and Employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Criteria period		3 years
Vesting period		3 years
PSUs \| Executives and Other Officers and Employees \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Core return threshold percentages		0.00%
PSUs \| Executives and Other Officers and Employees \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Core return threshold percentages		200.00%
Employee Stock \| ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for issuable (in shares)	200,000
Purchase price percentage of subsequent offering periods	95.00%
Maximum number of shares per participant (in shares)	725
Maximum worth of award per participant	$ 25
Shares issued under plan (in shares)	37,310,000	30,179,000	23,171,000
Number of shares reserved for issuance (in shares)	2,341,696	2,379,006

Share based compensation arrangement by share based payment award maximum purchase of common stock value per employee.

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- Definition

Share-based Compensation Arrangement By Share-based Payment Award, Number Of Shares Issued Upon Vesting Based On Core Return, Percentage

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Aggregate number of common shares reserved for future issuance.

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Carrying value as of the balance sheet date of dividends declared but unpaid on equity securities issued by the entity and outstanding.

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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.

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Amount of cost to be recognized for nonvested award under share-based payment arrangement. Excludes share and unit options.

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The cash inflow associated with the amount received from the stock plan during the period.

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Estimated period over which an employee is required to provide service in exchange for the equity-based payment award, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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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.

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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.

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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.

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The highest quantity of shares an employee can purchase under the plan per period.

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Number of shares authorized for issuance under share-based payment arrangement.

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Number of shares issued under share-based payment arrangement.

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Percentage of vesting of award under share-based payment arrangement.

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Purchase price of common stock expressed as a percentage of its fair value.

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