Note 1 - Description of Business and Summary of Significant Accounting Policies - Reconciliation of Basic to Diluted Weighted-average Shares Outstanding (Details) - shares shares in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Weighted average shares outstanding, basic (in shares)	96	99	88
Weighted average shares underlying stock options and restricted shares (in shares)	1	1	1
Weighted average shares outstanding, diluted (in shares)	97	100	89