Note 3 - Share-based Compensation - Components of Share-based Compensation (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Restricted Stock Units (RSUs) [Member]
Pretax compensation expense	$ 14,679	$ 9,741
Tax benefit	3,758	2,435
Share unit expense, net of tax	10,921	7,306
Performance Shares [Member]
Pretax compensation expense	3,384	3,830
Tax benefit	866	957
Share unit expense, net of tax	$ 2,518	$ 2,873

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
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
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