Income Taxes (Summary Of Tax Credit Carryforwards) (Details) $ in Thousands	Dec. 31, 2020 USD ($)
Tax Credit Carryforward [Line Items]
Total net operating loss amount	$ 120,309
Operating loss carryforward expiration year 2022
Tax Credit Carryforward [Line Items]
Net operating loss amount	99,596
Operating loss carryforward expiration year 2023
Tax Credit Carryforward [Line Items]
Net operating loss amount	5,853
Operating loss carryforward expiration year 2024
Tax Credit Carryforward [Line Items]
Net operating loss amount	3,566
Operating loss carryforward expiration year 2025 and beyond [Member]
Tax Credit Carryforward [Line Items]
Net operating loss amount	$ 11,294

Amount before allocation of valuation allowances of deferred tax asset attributable to deductible operating loss carryforwards.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32621-109319

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32632-109319

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 25
-Paragraph 20
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=117330534&loc=d3e28680-109314

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