Acquisitions and Sale of Businesses - Narrative on acquisitions of subsidiaries (Details) - USD ($) $ in Millions			3 Months Ended	12 Months Ended
	Jul. 03, 2023	Dec. 06, 2021	Dec. 31, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Business Acquisitions [Line Items]
Cash paid at purchase				$ 234	$ 10	$ 123
Finite-lived intangible assets useful life		10 years
Crop Risk Services
Business Acquisitions [Line Items]
Cash paid at purchase	$ 234
Net tangible assets acquired, at fair value	24
Acquisition costs incurred	3
Goodwill acquired during period	85			$ 85
Goodwill deductible for tax purposes	79
Crop Risk Services | Customer relationships
Business Acquisitions [Line Items]
Intangible assets acquired	124
Finite-lived intangible assets useful life				14 years
Crop Risk Services | Crop Insurance Contract, Crop Year 2022
Business Acquisitions [Line Items]
Gross written premiums	$ 1,200
Verikai, Inc.
Business Acquisitions [Line Items]
Cash paid at purchase		$ 120
Acquisition costs incurred		1
Intangible assets acquired		76
Goodwill acquired during period		70				$ 70
Total purchase price		$ 143
Insurance Agency
Business Acquisitions [Line Items]
Cash paid at purchase			$ 10
Total purchase price			$ 12