Separate accounts (Fair Value of Assets) (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Fair Value, Separate Account Investment [Line Items]
Separate account assets	$ 5,300	$ 5,190
Separate Account, Cash and Cash Equivalents
Fair Value, Separate Account Investment [Line Items]
Separate account assets	116	141
Separate Account, equity securities and mutual funds
Fair Value, Separate Account Investment [Line Items]
Separate account assets	5,082	4,960
Separate Account, Non-U.S. Government Treasuries
Fair Value, Separate Account Investment [Line Items]
Separate account assets	$ 102	$ 89

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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(11))
-URI https://asc.fasb.org/extlink&oid=126734703&loc=d3e572229-122910

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 80
-Section 50
-Paragraph 1
-Subparagraph (e)
-URI https://asc.fasb.org/extlink&oid=124508989&loc=d3e19393-158473

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 80
-Section 45
-Paragraph 2
-URI https://asc.fasb.org/extlink&oid=6484091&loc=d3e19268-158472

Reference 4: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 80
-Section 55
-Paragraph 17
-URI https://asc.fasb.org/extlink&oid=124505678&loc=SL117422397-158474

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