Note 4 - Redeemable, Convertible Preferred Stock (Details Textual) - USD ($) $ / shares in Units, $ in Millions			3 Months Ended
	Feb. 26, 2024	Feb. 26, 2021	Mar. 31, 2024	Dec. 31, 2023	Feb. 25, 2021
Preferred Stock, No Par Value (in dollars per share)			$ 0
Series C Preferred Stock [Member]
Embedded Derivative, Fair Value of Embedded Derivative Liability		$ 2
Series C Preferred Stock [Member] | After February Twenty Six Two Thousand Twenty Four [Member]
Temporary Equity, Convertible, Threshold Percentage of Stock Price Trigger	150.00%
Series C Preferred Stock [Member] | Minimum [Member]
Temporary Equity, Convertible, Threshold Trading Days (Day)			45 days
Series C Preferred Stock [Member] | Maximum [Member]
Temporary Equity, Convertible, Threshold Trading Days (Day)			60 days
Series C Preferred Stock [Member] | Other Noncurrent Liabilities [Member]
Embedded Derivative, Fair Value of Embedded Derivative Liability			$ 1	$ 1
Series B Preferred Stock [Member]
Embedded Derivative, Fair Value of Embedded Derivative Liability		$ 1
Preferred Stock, Dividend Rate, Percentage		4.00%
Preferred Stock, No Par Value (in dollars per share)		$ 0
Temporary Equity, Fair Value of Preferred Stock at Issuance		$ 95
Temporary Equity, Liquidation Preference Per Share (in dollars per share)		$ 100			$ 100
Debt Instrument, Convertible, Stock Price Trigger (in dollars per share)			$ 14.5
Series B Preferred Stock [Member] | Minimum [Member]
Temporary Equity, Convertible, Threshold Trading Days (Day)			45 days
Series B Preferred Stock [Member] | Maximum [Member]
Temporary Equity, Convertible, Threshold Trading Days (Day)			60 days
Repurchase And Exchange Agreement [Member] | Series A Preferred Stock [Member]
Stock Repurchased During Period, Shares (in shares)		1,000,000
Repurchase And Exchange Agreement [Member] | Series B Preferred Stock [Member]
Preferred Stock, Dividend Rate, Percentage		4.00%
Purchase Agreement [Member] | Series C Preferred Stock [Member]
Preferred Stock, Dividend Rate, Percentage		5.00%
Preferred Stock, No Par Value (in dollars per share)		$ 0
Temporary Equity, Liquidation Preference Per Share (in dollars per share)		100
Preferred Stock, Convertible, Conversion Price (in dollars per share)		$ 10
Stock Issued During Period, Shares, New Issues (in shares)		1,000,000
Shares Issued, Price Per Share (in dollars per share)		$ 100
Proceeds from Issuance or Sale of Equity		$ 100
Purchase Agreement [Member] | Series B Preferred Stock [Member]
Convertible Preferred Stock, Share Conversion, Rate (in shares)		9.5238
Preferred Stock, Convertible, Conversion Price (in dollars per share)		$ 10.5
Dividend And Other Rights [Member] | Series C Preferred Stock [Member]
Preferred Stock, Dividend Rate, Percentage		5.00%