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Note 2 - Fair Value Measurement - Fair Value of Assets Using Level 3 Input (Details) - Investments [Member] - USD ($)
$ in Millions
3 Months Ended 12 Months Ended
Mar. 31, 2020
Dec. 31, 2019
Beginning balance $ 1 $ 1
Purchases
Change in fair value recognized in net income
Total $ 1 $ 1