Stock Award Plans, Compensation Cost (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Stock Award Plans [Abstract]
Compensation cost	$ 14,722	$ 13,612	$ 19,104
Income tax benefit	$ 4,143	$ 3,368	$ 5,903

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
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-Publisher FASB
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