Note 6 - Redeemable, Convertible Preferred Stock (Details Textual) - USD ($) $ / shares in Units, $ in Millions	Feb. 26, 2024	Feb. 26, 2023	Feb. 26, 2021	Sep. 30, 2023	Dec. 31, 2022	Feb. 25, 2021
Preferred Stock, No Par Value (in dollars per share)				$ 0
Embedded Derivative, Fair Value of Embedded Derivative Liability				$ 2	$ 4
Series B Preferred Stock [Member]
Preferred Stock, Dividend Rate, Percentage			4.00%
Preferred Stock, No Par Value (in dollars per share)			$ 0
Preferred Stock Issued, Fair Value			$ 95
Temporary Equity, Liquidation Preference Per Share (in dollars per share)						$ 100
Preferred Stock, Convertible, Conversion Price (in dollars per share)			$ 14.5
Preferred Stock, Convertible, Threshold Trading Days			45
Preferred Stock, Convertible, Threshold Consecutive Trading Days			60
Embedded Derivative, Fair Value of Embedded Derivative Liability			$ 1	1	1
Series B Preferred Stock [Member] | Repurchase And Exchange Agreement [Member]
Stock Issued During Period, Shares, New Issues (in shares)			1,000,000
Preferred Stock, Dividend Rate, Percentage			4.00%
Series B Preferred Stock [Member] | Purchase Agreement [Member]
Convertible Preferred Stock, Shares Issued upon Conversion (in shares)			9.5238
Preferred Stock, Convertible, Conversion Price (in dollars per share)			$ 10.5
Series C Preferred Stock [Member]
Preferred Stock, Convertible, Threshold Trading Days		45	45
Preferred Stock, Convertible, Threshold Consecutive Trading Days		60	60
Embedded Derivative, Fair Value of Embedded Derivative Liability			$ 2
Series C Preferred Stock [Member] | Other Noncurrent Liabilities [Member]
Embedded Derivative, Fair Value of Embedded Derivative Liability				$ 1	$ 1
Series C Preferred Stock [Member] | After February Twenty Six Two Thousand Twenty Three [Member]
Debt Instrument, Convertible, Threshold Percentage of Stock Price Trigger		200.00%
Series C Preferred Stock [Member] | After February Twenty Six Two Thousand Twenty Four [Member] | Forecast [Member]
Debt Instrument, Convertible, Threshold Percentage of Stock Price Trigger	150.00%
Series C Preferred Stock [Member] | Purchase Agreement [Member]
Stock Issued During Period, Shares, New Issues (in shares)			1,000,000
Preferred Stock, Dividend Rate, Percentage			5.00%
Preferred Stock, Convertible, Conversion Price (in dollars per share)			$ 10
Shares Issued, Price Per Share (in dollars per share)			$ 100
Gross Proceeds From Issuance Of Preferred Stock And Preference Stock			$ 100
Gross Proceeds Owed on Issuance of PreferredStock			$ 100
Series C Preferred Stock [Member] | Dividend And Other Rights [Member]
Preferred Stock, Dividend Rate, Percentage			5.00%