Note 6 - Income Taxes - Deferred Tax Assets for Loss and Tax Credit Carryforwards (Details) $ in Millions	Dec. 31, 2023 USD ($)
Net operating losses	$ 274
Tax credits	1
Balance as of December 31, 2023	275
Tax Years 2024 Through 2028 [Member]
Net operating losses	63
Balance as of December 31, 2023	63
Tax Years 2029 Through 2033 [Member]
Net operating losses	38
Tax credits	1
Balance as of December 31, 2023	39
Tax Years 2034 Through 2038 [Member]
Net operating losses	33
Balance as of December 31, 2023	33
Indefinite [Member]
Net operating losses	140
Balance as of December 31, 2023	$ 140

Amount, before allocation of a valuation allowances, of deferred tax assets attributable to deductible tax credit carryforwards including, but not limited to, research, foreign, general business, alternative minimum tax, and other deductible tax credit carryforwards.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-6

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 8
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-8

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-3

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant