Note 8 - Stock-based Compensation - Stock-based Compensation Expense and Related Income Tax Benefit (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Stock-based compensation expense, gross	$ 16	$ 16	$ 7
Income tax benefit at our statutory rate associated with stock-based compensation	(4)	(4)	(2)
Stock-based compensation expense, net	$ 12	$ 12	$ 5

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

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