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Investment Information - Net realized gains and losses (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2025	Mar. 31, 2024
Available for sale securities:
Available for sale securities, gross gains on investment sales		$ 51	$ 50
Available for sale securities, gross losses on investment sales		(113)	(78)
Equity securities, at fair value:
Net realized gains (losses) on sales during the period		47	11
Net unrealized gains (losses) on equity securities still held at reporting date		(95)	82
Allowance for credit losses:
Allowance for credit losses - investments related		0	(6)
Allowance for credit losses - underwriting related		1	1
Derivative instruments	[1]	99	(10)
Other		(2)	17
Net realized gains (losses)		3	67
Fixed maturities
Available for sale securities:
Change in fair value of assets and liabilities accounted for using the fair value option		2	2
Other investments
Available for sale securities:
Change in fair value of assets and liabilities accounted for using the fair value option		$ 13	$ (2)
[1] See note 10 for information on the Company’s derivative instruments.

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