Earnings Per Common Share and Share Awards (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Common Share And Share Awards [Line Items]
Incremental dilutive potential common shares, calculated using treasury stock method (in shares)	8	10	10
Anti-dilutive shares excluded from computation of diluted earnings per share	14	9	4
Options and SARs vested	4
Fair value of options and SARs vested	$ 264
Weighted-average fair values for SARs issued (dollars per share)	$ 51.88	$ 78.61	$ 55.40
Number of stock options or SARs granted where exercise price was less than market price on date of grant	0
Compensation expense relating to SARs or options vesting	$ 264	$ 327	$ 219
Total unrecognized compensation cost related to unvested share-based compensation arrangements granted under stock award plans	$ 58
Weighted-average period of unrecognized compensation cost recognition	3 months
Maximum
Earnings Per Common Share And Share Awards [Line Items]
Maximum shares of Company stock to be granted to key employees or directors	250
SARs
Earnings Per Common Share And Share Awards [Line Items]
Intrinsic values of options exercised	$ 364	$ 153	$ 473

Earnings Per Common Share And Share Awards [Line Items]

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Number of stock options or SARs granted where exercise price was less than market price on date of grant.

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Share-based Compensation Arrangement by Share-based Payments Award, Options And Equity Instruments Other Than Options Vested In Period

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

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Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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

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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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Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of share based payment arrangements using the treasury stock method.

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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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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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Number of shares purchased for issuance under share-based payment arrangement.

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