Investments - Schedule of changes in unrealized appreciation (depreciation) of available for sale securities and other investments (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Increase (decrease) in unrealized appreciation (depreciation) of investments	$ 8,440	$ (47,766)	$ (9,255)
Unrealized gains (losses) recognized during the reporting period on equity securities and other investments still held at the reporting date
Net gains (losses) recognized during the period on equity securities and other investments	583	302
Less: Net gains (losses) recognized during the period on equity securities and other investments sold during the period	143	73
Unrealized gains (losses) recognized during the reporting period on equity securities and other investments still held at the reporting date	440	229
Continuing Operations, Excluding Held-For-Sale
Debt Securities, Available-for-sale [Line Items]
Increase (decrease) in unrealized appreciation (depreciation) of investments	8,511	(47,766)
Fixed maturity securities | Continuing Operations, Excluding Held-For-Sale
Debt Securities, Available-for-sale [Line Items]
Increase (decrease) in unrealized appreciation (depreciation) of investments	8,511	(47,741)
Other investments | Continuing Operations, Excluding Held-For-Sale
Debt Securities, Available-for-sale [Line Items]
Increase (decrease) in unrealized appreciation (depreciation) of investments	0	(25)
Equity securities
Unrealized gains (losses) recognized during the reporting period on equity securities and other investments still held at the reporting date
Net gains (losses) recognized during the period on equity securities and other investments	94	(53)
Less: Net gains (losses) recognized during the period on equity securities and other investments sold during the period	163	96
Unrealized gains (losses) recognized during the reporting period on equity securities and other investments still held at the reporting date	(69)	(149)
Other invested assets
Unrealized gains (losses) recognized during the reporting period on equity securities and other investments still held at the reporting date
Net gains (losses) recognized during the period on equity securities and other investments	489	355
Less: Net gains (losses) recognized during the period on equity securities and other investments sold during the period	(20)	(23)
Unrealized gains (losses) recognized during the reporting period on equity securities and other investments still held at the reporting date	$ 509	$ 378