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Share based compensation arrangement by share based payment award conversion of outstanding stock options.

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The Maximum Option vested as percentage of total option grant during the year.

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The period of performance for options under LTIP.

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Unrecognized compensation expense of reporting period.

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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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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 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 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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The highest percentage of annual salary that an employee is permitted to utilize with respect to the plan.

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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.

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Gross number of share options (or share units) granted during the period.

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Number of options outstanding, including both vested and non-vested options.

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Number of new stock issued during the period.

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Stock Compensation Plans - Additional information (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number			36,261	17,700
Conversion of outstanding stock options			39,983
Share-based Compensation Arrangement by Share-based Payment Award, Maximum Vested Percentage, Year			20.00%
Stock Option Period, Description			All options expire ten years from the date of grant. Vested options of retirees expire on the earlier of the scheduled expiration date or three months after the retirement date.
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross			0	0
Employee Service Share Based Compensation Nonvested Awards, Total Compensation Cost Not Yet Recognized, Period For Recognition (in years)			1 month
Allocated Share-based Compensation Expense			$ 2.3	$ 2.1	$ 2.0
Compensation Expense, Maximum			2.4
Estimated Compensation Expense, Excepted			1.6
Unrecognized Compensation Expense			$ 1.0
Executive Long-Term Equity Incentive Plan [Member]
Stock Option Period, Description			The amount of benefit under the remaining 2020 LTIP will be determined individually at the end of the 36 month performance period ending December 31. The benefits earned under this LTIP will be paid out in equity in the first quarter following the end of the performance period. The participants are required to be employed on the day of payout in order to receive the payment
Share-based Compensation, Performance Period			3 years
Common stock issued during the period	32,288		51,677
Executive Long-Term Equity Incentive Plan [Member] \| Forecast [Member]
Common stock issued during the period		21,834
Executive Long-Term Equity Incentive Plan [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Maximum Employee Subscription Rate			20.00%
Executive Long-Term Equity Incentive Plan [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Maximum Employee Subscription Rate			45.00%
Equity Plan 2018 [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized			900,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant			695,869
Short Term Equity Incentive Plan 2015 [Member]
Stock Option Period, Description			The final amount of benefits under the STIPs is determined as of December 31 of the same year and paid out in cash in the first quarter of the following year.
Performance Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross			100,714
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number			90,891
Performance Stock Units [Member] \| Executive Long-Term Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross			100,714
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross			13,548
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross			1,510
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period			3 years
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number			55,759	158,470
Restricted Stock Units (RSUs) [Member] \| Executive Long-Term Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross				69,014	41,676
Restricted Stock Units (RSUs) [Member] \| Key Long-Term Equity Incentive Plan 2015 [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	12,038
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period			3 years
Restricted Stock Units (RSUs) [Member] \| Key Long-Term Equity Incentive Plan 2015 [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Maximum Employee Subscription Rate			5.00%
Restricted Stock Units (RSUs) [Member] \| Key Long-Term Equity Incentive Plan 2015 [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Maximum Employee Subscription Rate			10.00%
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross			14,859
Restricted Stock Grants [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross			13,349
Restricted Stock Grants [Member] \| Share-based Compensation Award, Tranche One [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross			13,349
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period			1 year
Restricted Share Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number			187,707
Short Term Incentive Plan [Member]
Allocated Share-based Compensation Expense			$ 3.2	$ 1.2
Long Term Equity Incentive Plan 2015 [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant			126,758