Separate accounts (Fair Value of Assets) (Details) - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022
Fair Value, Separate Account Investment [Line Items]
Separate account assets	$ 5,574	$ 5,190
Separate Account, Cash and Cash Equivalents
Fair Value, Separate Account Investment [Line Items]
Separate account assets	98	141
Separate Account, equity securities and mutual funds
Fair Value, Separate Account Investment [Line Items]
Separate account assets	5,382	4,960
Separate Account, Non-U.S. Government Treasuries
Fair Value, Separate Account Investment [Line Items]
Separate account assets	$ 94	$ 89

Amount of asset at fair value held for benefit of separate account policyholder.

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 944
-SubTopic 80
-Name Accounting Standards Codification
-Section 55
-Paragraph 17
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480078/944-80-55-17

Reference 2: 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)(11))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479440/944-210-S99-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 80
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480141/944-80-45-2

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 80
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480109/944-80-50-1

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