Derivative Financial Instruments (Summary Of Outstanding Fair Value Hedges) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Derivative [Line Items]
Derivative, notional amount	$ 785	$ 1,335
Interest Rate Swaps [Member]
Derivative [Line Items]
Derivative, notional amount	575	1,200
Interest Rate Swaps [Member] \| Interest Rate Received Four Point One Zero One Percentage [Member] \| 2020 [Member]
Derivative [Line Items]
Derivative, notional amount	$ 75	0
Interest Rate Received	4.101%
Expiration Date	Sep. 01, 2027
Interest Rate Swaps [Member] \| Interest Rate Received Four Point One Zero One Percentage [Member] \| 2018 [Member]
Derivative [Line Items]
Derivative, notional amount	$ 50	$ 50
Interest Rate Received	4.101%	4.101%
Expiration Date	Sep. 01, 2027	Sep. 01, 2027
Interest Rate Swaps [Member] \| Interest Rate Received Three Point Three Zero Percentage [Member] \| 2018 [Member]
Derivative [Line Items]
Derivative, notional amount	$ 450	$ 450
Interest Rate Received	3.30%	3.30%
Expiration Date	Jan. 15, 2023	Jan. 15, 2023
Interest Rate Swaps [Member] \| Interest Rate Received Four Point Three Five Percentage [Member] \| 2018 [Member]
Derivative [Line Items]
Derivative, notional amount	$ 0	$ 90
Interest Rate Received	4.35%	4.35%
Expiration Date	Aug. 15, 2020	Aug. 15, 2020
Interest Rate Swaps [Member] \| Interest Rate Received Four Point Three Five Percentage [Member] \| 2017 [Member]
Derivative [Line Items]
Derivative, notional amount	$ 0	$ 50
Interest Rate Received	4.35%	4.35%
Expiration Date	Aug. 15, 2020	Aug. 15, 2020
Interest Rate Swaps [Member] \| Interest Rate Received Four Point Three Five Percentage [Member] \| 2015 [Member]
Derivative [Line Items]
Derivative, notional amount	$ 0	$ 200
Interest Rate Received	4.35%	4.35%
Expiration Date	Aug. 15, 2020	Aug. 15, 2020
Interest Rate Swaps [Member] \| Interest Rate Received Four Point Three Five Percentage [Member] \| 2014 [Member]
Derivative [Line Items]
Derivative, notional amount	$ 0	$ 150
Interest Rate Received	4.35%	4.35%
Expiration Date	Aug. 15, 2020	Aug. 15, 2020
Interest Rate Swaps [Member] \| Interest Rate Received Four Point Three Five Percentage [Member] \| 2013 [Member]
Derivative [Line Items]
Derivative, notional amount	$ 0	$ 10
Interest Rate Received	4.35%	4.35%
Expiration Date	Aug. 15, 2020	Aug. 15, 2020
Interest Rate Swaps [Member] \| Interest Rate Received Four Point Three Five Percentage [Member] \| 2012 [Member]
Derivative [Line Items]
Derivative, notional amount	$ 0	$ 200
Interest Rate Received	4.35%	4.35%
Expiration Date	Aug. 15, 2020	Aug. 15, 2020

Fixed interest rate related to the interest rate derivative.

No definition available.

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- Definition

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

No definition available.

+ Details

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- Definition

Nominal or face amount used to calculate payment on derivative.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5580258-113959

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5579245-113959

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- Definition

Expiration date of the open option contracts written on the investment, in CCYY-MM-DD format.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 320
-Section S99
-Paragraph 5
-Subparagraph (SX 210.12-13(Column F))
-URI http://asc.fasb.org/extlink&oid=120401592&loc=d3e611282-123010

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