Investments (Securities Lending - Narrative) (Details) $ in Millions	Sep. 30, 2023 USD ($)
Investments, Debt and Equity Securities [Abstract]
Cash collateral on deposit from counterparties	$ 699
Percentage of reinvestment portfolio invested in liquid assets	58.00%

Amount of securities loaned to entities in exchange for collateral, not subject to a master netting arrangement.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (d)
-SubTopic 20
-Topic 210
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483466/210-20-50-3

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 22
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483444/210-20-55-22

Name:	us-gaap_SecuritiesLoanedNotSubjectToMasterNettingArrangement
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant