Stock-Based Compensation Plans - Stock Options (Details) - USD ($)	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense	$ 0
Outstanding stock options (in shares)	80,000
Weighted average exercise price (in USD per share)	$ 27.70
Share-based Payment Arrangement, Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options expense	$ 100,000	$ 100,000

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

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Amount of cost to be recognized for option under share-based payment 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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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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The number of shares reserved for issuance pertaining to the outstanding stock options as of the balance sheet date for all option plans in the customized range of exercise prices.

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