Note 8 - Stock-based Compensation - Stock-based Compensation Expense and Related Income Tax Benefit (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Stock-based compensation expense, gross	$ 3	$ 5	$ 10	$ 12
Income tax benefit at our statutory rate associated with share-based compensation	(1)	(1)	(3)	(3)
Stock-based compensation expense, net	$ 2	$ 4	$ 7	$ 9

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

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