Stock-Based Compensation Plans (Schedule of Compensation Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Restricted Stock Units (RSUs) [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Compensation expense(1)	$ 475	$ 389	$ 263
Income tax benefit	102	84	57
Fair value of grants vested	407	302	149
Restricted Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Compensation expense(1)	781	751	916
Income tax benefit	168	161	197
Fair value of grants vested	772	780	931
Management Stock Purchase Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Compensation expense(1)	71	95	104
Income tax benefit	15	20	22
Fair value of grants vested	110	75	130
Performance Shares [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Compensation expense(1)	332	532	291
Income tax benefit	71	114	63
Fair value of grants vested	0	344	284
Deferred Stock Awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Compensation expense(1)	122	110	106
Income tax benefit	26	24	23
Fair value of grants vested	$ 129	$ 102	$ 105

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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
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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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