Stock Award Plans, Compensation Cost (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Stock Award Plans [Abstract]
Compensation cost	$ 3,645	$ 3,414	$ 12,793	$ 12,066
Income tax benefit	$ 1,068	$ 1,181	$ 3,660	$ 3,332

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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
-Topic 718
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-Section 50
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-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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