Long duration insurance contracts - Summary of gross premiums earned and interest expense (Detail) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2023	Mar. 31, 2022
Periodic Payment Annuities [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums		$ 169
Interest Expense	$ 133	135
Life and Health [Member]
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	1,004	1,143
Interest Expense	$ 54	$ 53

Amount of gross premium income recognized for liability for future policy benefit.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 50
-Paragraph 6
-Subparagraph (b)(3)
-URI https://asc.fasb.org/extlink&oid=124506351&loc=d3e14931-158439

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 55
-Paragraph 29E
-URI https://asc.fasb.org/extlink&oid=126561865&loc=SL117819541-158441

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 50
-Paragraph 6
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=124506351&loc=d3e14931-158439

Name:	us-gaap_LiabilityForFuturePolicyBenefitGrossPremiumIncome
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration