Share-based Compensation - Restricted Shares and RSUs (Details) - Restricted Shares and RSUs - $ / shares	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award
Vesting period	4 years
Number of Awards
Unvested, beginning balance (in shares)	589,587	484,808	369,477
Granted (in shares)	341,508	259,992	259,812
Vested (in shares)	(229,226)	(141,556)	(96,630)
Forfeited (in shares)	(22,610)	(13,657)	(47,851)
Unvested, ending balance (in shares)	679,259	589,587	484,808
Weighted Average Grant Date Fair Value
Unvested, beginning balance (usd per share)	$ 22.96	$ 23.34	$ 23.70
Granted (usd per share)	22.61	22.04	22.76
Vested (usd per share)	22.82	22.56	23.30
Forfeited (usd per share)	22.77	23.00	23.05
Unvested, ending balance (usd per share)	$ 22.84	$ 22.96	$ 23.34
First period
Share-based Compensation Arrangement by Share-based Payment Award
Vesting period	1 year

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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The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options.

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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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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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