Income Taxes (Summary Of Detail Of Tax Carryforwards) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Income Tax Contingency [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards, State and Local	$ 58	$ 50
Operating Loss Carryforwards, Valuation Allowance	(31)
Deferred Tax Assets, Net	27
Tax credit acquired in an acquisition [Member] \| State Tax Authority [Member]
Income Tax Contingency [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards, State and Local	2
Net Operating Losses Federal Date Range 1
Income Tax Contingency [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards, State and Local	18
Operating Loss Carryforwards, Valuation Allowance	0
Deferred Tax Assets, Net	18
Pre Tax Earnings Necessary To Realize	87
Net Operating Losses Federal Date Range 2
Income Tax Contingency [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards, State and Local	7
Operating Loss Carryforwards, Valuation Allowance	0
Deferred Tax Assets, Net	7
Net Operating Losses States Date Range One [Member]
Income Tax Contingency [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards, State and Local	14
Operating Loss Carryforwards, Valuation Allowance	(14)
Deferred Tax Assets, Net	0
Pre Tax Earnings Necessary To Realize	0
Net Operating Losses States Date Range Two [Member]
Income Tax Contingency [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards, State and Local	13
Operating Loss Carryforwards, Valuation Allowance	(12)
Deferred Tax Assets, Net	1
Pre Tax Earnings Necessary To Realize	8
Net Operating Losses States Date Range Three [Member]
Income Tax Contingency [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards, State and Local	4
Operating Loss Carryforwards, Valuation Allowance	(3)
Deferred Tax Assets, Net	1
Pre Tax Earnings Necessary To Realize	23
Other Credits States Date Range One [Member]
Income Tax Contingency [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards, State and Local	2
Operating Loss Carryforwards, Valuation Allowance	(2)
Deferred Tax Assets, Net	0
Federal Tax Authority [Member] \| Tax credit acquired in an acquisition [Member]
Income Tax Contingency [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards, State and Local	$ 25

Pre-Tax Earnings Necessary to Realize

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- Definition

Amount, after allocation of valuation allowances and deferred tax liability, of deferred tax asset attributable to deductible differences and carryforwards, without jurisdictional netting.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32537-109319

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

+ References

Reference 1: 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 2: http://www.xbrl.org/2009/role/commonPracticeRef
-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

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

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- Definition

The portion of the valuation allowance pertaining to the deferred tax asset representing potential future taxable deductions from net operating loss carryforwards for which it is more likely than not that a tax benefit will not be realized.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 2
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