Income Taxes, Tax Credit Carryforwards (Details) $ in Millions	Dec. 31, 2020 USD ($)
Federal [Member]
Operating Loss Carryforwards [Abstract]
Net operating loss carryforwards	$ 243.3
Federal [Member] \| Research and Development [Member]
Tax Credit Carryforwards [Abstract]
Tax credit carryforwards	210.5
California [Member]
Operating Loss Carryforwards [Abstract]
Net operating loss carryforwards	346.3
California [Member] \| Research and Development [Member]
Tax Credit Carryforwards [Abstract]
Tax credit carryforwards	$ 87.4

Amount of operating loss carryforward, before tax effects, available to reduce future taxable income under enacted tax laws.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32559-109319

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