Note 1 - Description of Business and Summary of Significant Accounting Policies - Trade Revenue and Expense (Details) - USD ($) $ in Millions |
12 Months Ended | ||
---|---|---|---|
Dec. 31, 2020 |
Dec. 31, 2019 |
Dec. 31, 2018 |
|
Trade revenue | $ 5 | $ 8 | $ 3 |
Trade expense | (5) | (8) | (3) |
Net trade income (loss) | $ 0 | $ 0 | $ 0 |