Unaudited Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Millions	Total	Non-cumulative preferred shares	Common shares	Additional paid-in capital	Retained earnings	Accumulated other comprehensive income (loss), net of deferred income tax	Unrealized appreciation (decline) in value of available-for-sale securities, net of deferred income tax	Foreign currency translation adjustments, net of deferred income tax	Common shares held in treasury, at cost
Balance at beginning of period at Dec. 31, 2022		$ 830	$ 1	$ 2,211	$ 15,892	$ (1,646)	$ (1,512)	$ (134)	$ (4,378)
Amortization of share-based compensation				73
Other changes				13
Net income (loss)	$ 2,109				2,109
Preferred share dividends	(30)				(30)
Unrealized holding gains (losses) during period, net of reclassification adjustment							226
Foreign currency translation adjustments	(33)							(33)
Shares repurchased for treasury									(29)
Balance at end of period at Sep. 30, 2023	15,239	830	1	2,297	17,971	(1,453)	(1,286)	(167)	(4,407)
Balance at beginning of period at Jun. 30, 2023		830	1	2,278	17,258	(1,319)	(1,192)	(127)	(4,407)
Amortization of share-based compensation				15
Other changes				4
Net income (loss)	723				723
Preferred share dividends	(10)				(10)
Unrealized holding gains (losses) during period, net of reclassification adjustment							(94)
Foreign currency translation adjustments	(40)							(40)
Shares repurchased for treasury									0
Balance at end of period at Sep. 30, 2023	15,239	830	1	2,297	17,971	(1,453)	(1,286)	(167)	(4,407)
Balance at beginning of period at Dec. 31, 2023	18,353	830	1	2,327	20,295	(676)	(565)	(111)	(4,424)
Amortization of share-based compensation				100
Other changes				38
Net income (loss)	3,377				3,377
Preferred share dividends	(30)				(30)
Unrealized holding gains (losses) during period, net of reclassification adjustment							500
Foreign currency translation adjustments	(24)							(24)
Shares repurchased for treasury									(40)
Balance at end of period at Sep. 30, 2024	22,274	830	1	2,465	23,642	(200)	(65)	(135)	(4,464)
Balance at beginning of period at Jun. 30, 2024		830	1	2,443	22,664	(810)	(650)	(160)	(4,463)
Amortization of share-based compensation				16
Other changes				6
Net income (loss)	988				988
Preferred share dividends	(10)				(10)
Unrealized holding gains (losses) during period, net of reclassification adjustment							585
Foreign currency translation adjustments	25							25
Shares repurchased for treasury									(1)
Balance at end of period at Sep. 30, 2024	$ 22,274	$ 830	$ 1	$ 2,465	$ 23,642	$ (200)	$ (65)	$ (135)	$ (4,464)