Acquisitions of Businesses - Allocation of the purchase price of subsidiary (Details) - USD ($) $ in Millions		12 Months Ended
	Jul. 03, 2023	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Business Acquisitions [Line Items]
Cash paid at purchase		$ 9	$ 234	$ 10
Crop Risk Services
Business Acquisitions [Line Items]
Cash paid at purchase	$ 234
Tangible assets acquired:
Cash and cash equivalents	26
Agents’ balances and premiums receivable	164
Other assets	3
Total tangible assets acquired	193
Liabilities acquired:
Other liabilities	169
Total liabilities acquired	169
Net tangible assets acquired, at fair value	24
Excess purchase price over net tangible assets acquired	210
Deferred tax asset acquired	1
Goodwill acquired during period	85		$ 85
Crop Risk Services | Customer relationships
Liabilities acquired:
Intangible assets acquired	$ 124