Debt (Narrative) (Details) - Delaware Trust Facility [Member]	9 Months Ended
Sep. 30, 2020 USD ($)
Debt Instrument [Line Items]
Facility agreement term	10 years
Pre-capitalized securities, sold by trust	$ 500,000,000
Facility fee rate	1.691%
Stockholders' equity threshold triggering required facility exercise	$ 2,750,000,000
Potential Issuance In Exchange For US Treasury Securities [Member] \| Senior Notes 2.330%, Due 2030 [Member]
Debt Instrument [Line Items]
Principal balance	$ 500,000,000
Interest rate	2.33%

Facility Agreement Term

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- Definition

Pre-capitalized securities, sold by trust

+ References

No definition available.

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- Definition

Stockholders' equity threshold triggering required facility exercise

+ References

No definition available.

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- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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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

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- Definition

The fee, expressed as a percentage of the line of credit facility, for the line of credit facility regardless of whether the facility has been used.

+ References

No definition available.

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