Common Stock Incentive Plan - Performance Shares and Restricted Stock Units (Details) $ in Millions	9 Months Ended
Sep. 30, 2021 USD ($) shares
Performance Shares and Restricted Stock Units
Common Stock Incentive Plan
Unamortized share-based compensation expense \| $	$ 12.7
Performance Shares
Common Stock Incentive Plan
Shares granted in period (in shares)	157,341
Shares forfeited (in shares)	9,621
Vesting rights percentage	50.00%
Vesting period (in years)	3 years
Performance Shares \| 2021 grants
Common Stock Incentive Plan
Grants outstanding (in shares)	147,720
Restricted Stock Units
Common Stock Incentive Plan
Shares granted in period (in shares)	17,285
Vesting period (in years)	4 years

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

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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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