Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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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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Represents the performance cycle on conclusion of which shares become payable.

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Employee Share-Based Incentive Compensation Plans - Narrative (Details) $ in Millions	3 Months Ended		36 Months Ended
	Mar. 31, 2022 USD ($) shares	Mar. 31, 2021 USD ($) shares	Dec. 31, 2021 USD ($) shares	Dec. 31, 2020 USD ($)
Performance Share \| W T M Incentive Plan
Share-based compensation arrangement by share-based payment award
Vesting period	3 years
Performance cycle period	3 years
New grants (in shares) \| shares	13,075	13,000	750
Additional compensation cost that would be recognized if all outstanding performance shares vested \| $	$ 25.8
Performance Share \| Minimum \| W T M Incentive Plan
Share-based compensation arrangement by share-based payment award
Share-based compensation arrangement by share-based payment award, multiplier	0
Performance Share \| Maximum \| W T M Incentive Plan
Share-based compensation arrangement by share-based payment award
Share-based compensation arrangement by share-based payment award, multiplier	2
Restricted Stock
Share-based compensation arrangement by share-based payment award
Vesting period	34 months
Restricted Stock \| W T M Incentive Plan
Share-based compensation arrangement by share-based payment award
Additional compensation cost that would be recognized if all outstanding performance shares vested \| $	$ 26.5	$ 26.2	$ 15.9	$ 15.2
Issued (in shares) \| shares	13,075	13,000