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, 2021		$ 830	$ 1	$ 2,085	$ 14,456	$ (65)	$ 13	$ (78)	$ (3,761)
Amortization of share-based compensation				80
Other changes				22
Net income (loss)	$ 620				620
Net (income) loss attributable to noncontrolling interests	(3)				(3)
Preferred share dividends	(30)				(30)
Unrealized holding gains (losses) during period, net of reclassification adjustment							(1,686)
Foreign currency translation adjustments	(141)							(141)
Shares repurchased for treasury									(612)
Balance at end of period at Sep. 30, 2022	11,796	830	1	2,187	15,043	(1,892)	(1,673)	(219)	(4,373)
Balance at beginning of period at Jun. 30, 2022		830	1	2,170	15,036	(1,258)	(1,109)	(149)	(4,361)
Amortization of share-based compensation				14
Other changes				3
Net income (loss)	18				18
Net (income) loss attributable to noncontrolling interests	(1)				(1)
Preferred share dividends	(10)				(10)
Unrealized holding gains (losses) during period, net of reclassification adjustment							(564)
Foreign currency translation adjustments	(70)							(70)
Shares repurchased for treasury									(12)
Balance at end of period at Sep. 30, 2022	11,796	830	1	2,187	15,043	(1,892)	(1,673)	(219)	(4,373)
Balance at beginning of period at Dec. 31, 2022	12,910	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
Net (income) loss attributable to noncontrolling interests	0				0
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
Net (income) loss attributable to noncontrolling interests	0				0
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)