Period of performance under the deferred compensation arrangement.

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Represents the percentage of the original grant (target number) of performance share awards that will be earned and vested.

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Represents the percentage of the original grant (target number) of performance share units that will be earned and vested.

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Period from vesting date after which transfer restrictions on an employee's award lapse, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The ratio of shares of common stock issued for each vested equity-based payment instrument, excluding stock (or unit) options.

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Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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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 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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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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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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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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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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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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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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No definition available.

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

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Stock-Based Compensation - Performance Share Units and Performance Share Awards (Details) $ / shares in Units, $ in Thousands				12 Months Ended
	Jan. 01, 2020 $ / shares shares	Jan. 01, 2019 $ / shares shares	Jan. 01, 2018 $ / shares shares	Dec. 31, 2020 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2017 $ / shares shares	Dec. 31, 2016 shares
Stock-based compensation
Stock-based compensation expense \| $				$ 10,000	$ 7,800	$ 6,900
Period for recognition of unrecognized compensation expense				1 year 1 month 6 days
Performance Share Units
Stock-based compensation
Ratio of common stock for each vested award				1
Number of Shares
Unvested as of beginning of period (in shares)	695,316	504,497	506,051	695,316	504,497	506,051
Granted (in shares)				340,758	310,696	277,197
Vested (in shares)				(172,167)	(36,342)	(229,809)
Forfeited (in shares)				(6,625)	(83,535)	(48,942)
Unvested as of end of period (in shares)				857,282	695,316	504,497	506,051
Weighted Average Grant Date Fair Value
Unvested as of beginning of period (in dollars per share) \| $ / shares	$ 26.46	$ 25.93	$ 30.82	$ 26.46	$ 25.93	$ 30.82
Granted (in dollars per share) \| $ / shares				25.96	27.04	22.39
Vested (in dollars per share) \| $ / shares				29.95	24.51	32.17
Forfeited (in dollars per share) \| $ / shares				26.13	26.37	30.52
Unvested as of end of period (in dollars per share) \| $ / shares				$ 25.43	$ 26.46	$ 25.93	$ 30.82
Stock-based compensation
Unrecognized compensation expense \| $				$ 6,200	$ 5,600	$ 6,200
Period for recognition of unrecognized compensation expense				1 year 1 month 6 days
Total fair value of vested shares (in dollars) \| $				$ 5,200	$ 900	$ 7,400
Performance Share Units \| Key employees
Number of Shares
Granted (in shares)				340,758	310,696	277,197
Minimum
Stock-based compensation
Performance achieved, percentage of PSUs earned and vested				0
Performance achieved, percentage of PSAs earned and vested				0
Maximum
Stock-based compensation
Performance achieved, percentage of PSUs earned and vested				100
Performance achieved, percentage of PSAs earned and vested				200
IPO \| Performance Share Units
Number of Shares
Granted (in shares)								115,566
Stock-based compensation
Period following vesting date for lapsing of transfer restrictions							6 months
IPO \| Performance Share Units \| Tranche one
Stock-based compensation
Vesting (as a percent)								33.33%
IPO \| Performance Share Units \| Tranche two
Stock-based compensation
Vesting (as a percent)								33.33%
IPO \| Performance Share Units \| Tranche three
Stock-based compensation
Vesting (as a percent)								33.33%
LongTerm Incentive Plan
Stock-based compensation
Performance period	3 years	3 years	3 years	3 years