Investments (Details) - Investment Information, Equity Securities - USD ($) $ in Millions	9 Months Ended	12 Months Ended
Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Investment disclosure details
Equity securities, cost	$ 546		$ 747
Gross gains	67		92
Gross losses	40		32
Equity securities, at fair value	573		807
Net recognized losses on equity securities still held	11	$ 110
Common stock [Member]
Investment disclosure details
Equity securities, cost	502		706
Gross gains	65		89
Gross losses	40		32
Equity securities, at fair value	527		763
Non-redeemable preferred stock [Member]
Investment disclosure details
Equity securities, cost	44		41
Gross gains	2		3
Gross losses	0		0
Equity securities, at fair value	$ 46		$ 44

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Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(1)(b))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479440/944-210-S99-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(2))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1A
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482736/825-10-45-1A

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Amount of unrealized gain on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 321
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479536/321-10-50-4

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Amount of unrealized gain (loss) on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(3)(d)(2))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483586/944-220-S99-1

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-Topic 321
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-Section 50
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479536/321-10-50-4

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