Investments - Summary of Sources of Collateral Received and Various Investment Agreement in which Collateral Pledged (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Investment [Line Items]
Fair Value Of Securities Deposited With Governmental Authorities	$ 24	$ 23
Fair Value of Securities Deposited in Connection wtih Letter of Credit	$ 1	1
Standard & Poor's, B Rating [Member]
Investment [Line Items]
Investment Owned, at Fair Value		403
Standard & Poor's, B Rating [Member] \| Municipal Bonds [Member]
Investment [Line Items]
Investment Owned, at Fair Value		10
Standard & Poor's, B Rating [Member] \| Mortgage And Other Asset Backed Securities [Member]
Investment [Line Items]
Investment Owned, at Fair Value		$ 394

Value of the investment at close of period. For schedules of investments that are categorized, the value would be aggregated by category. For investment in and advances to affiliates, if operations of any controlled companies are different in character from those of the company, group such affiliates within divisions and by type of activities.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 210
-Section 50
-Paragraph 6
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=99383244&loc=d3e12121-115841

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 320
-Section S99
-Paragraph 5D
-Subparagraph (SX 210.12-13D(Column C))
-URI https://asc.fasb.org/extlink&oid=122147990&loc=SL120429264-123010

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 320
-Section S99
-Paragraph 3
-Subparagraph (SX 210.12-12B(Column C))
-URI https://asc.fasb.org/extlink&oid=122147990&loc=d3e611197-123010

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