Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Thousands	Total	Non-cumulative preferred shares	Common shares	Additional paid-in capital	Retained earnings	Retained earnings Cumulative Effect, Period of Adoption, Adjustment	Retained earnings Cumulative Effect, Period of Adoption, Adjusted Balance	Accumulated other comprehensive income (loss)	Unrealized appreciation (decline) in value of available-for-sale investments, 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 year at Dec. 31, 2019		$ 780,000	$ 638	$ 1,889,683	$ 11,021,006	$ (22,452)	$ 10,998,554	$ 212,091	$ 258,486	$ (46,395)	$ (2,406,047)
Preferred shares issued		0
Preferred shares redeemed		0
Common shares issued, net			5
Issue costs on preferred shares issued				0
Loss on redemption of preferred shares	$ 0			0	0
Amortization of share-based compensation				70,535
Other changes				17,576
Net income	1,465,711				1,465,711
Net (income) loss attributable to noncontrolling interests	(60,190)				(60,190)
Preferred share dividends	(41,612)				(41,612)
Unrealized holding gains (losses) during period, net of reclassification adjustment									252,530
Unrealized holding gains (losses) during period attributable to noncontrolling interests									(9,721)
Foreign currency translation adjustments	33,336									33,336
Foreign currency translation adjustments attributable to noncontrolling interests										659
Shares repurchased for treasury	(83,472)										(97,862)
Balance at end of year at Dec. 31, 2020	$ 13,105,886	780,000	643	1,977,794	12,362,463	0	12,362,463	488,895	501,295	(12,400)	(2,503,909)
Accounting Standards Update [Extensible Enumeration]	Accounting Standards Update 2016-13 [Member]
Non-redeemable noncontrolling interests	$ 823,007
Total shareholders' equity	13,928,893
Preferred shares issued		500,000
Preferred shares redeemed		(450,000)
Common shares issued, net			5
Issue costs on preferred shares issued				(14,179)
Loss on redemption of preferred shares	(15,101)			15,101	(15,101)
Amortization of share-based compensation				86,053
Other changes				20,306
Net income	2,239,462				2,239,462
Net (income) loss attributable to noncontrolling interests	(82,613)				(82,613)
Preferred share dividends	(48,343)				(48,343)
Unrealized holding gains (losses) during period, net of reclassification adjustment									(502,997)
Unrealized holding gains (losses) during period attributable to noncontrolling interests									15,188
Foreign currency translation adjustments	(64,482)									(64,482)
Foreign currency translation adjustments attributable to noncontrolling interests										(1,204)
Shares repurchased for treasury	(1,234,294)										(1,257,186)
Balance at end of year at Dec. 31, 2021	13,545,896	830,000	648	2,085,075	14,455,868	$ 0	$ 14,455,868	(64,600)	13,486	(78,086)	(3,761,095)
Non-redeemable noncontrolling interests	0
Total shareholders' equity	13,545,896
Preferred shares issued		0
Preferred shares redeemed		0
Common shares issued, net			6
Issue costs on preferred shares issued				0
Loss on redemption of preferred shares	0			0	0
Amortization of share-based compensation				87,620
Other changes				38,749
Net income	1,482,423				1,482,423
Net (income) loss attributable to noncontrolling interests	(5,490)				(5,490)
Preferred share dividends	(40,736)				(40,736)
Unrealized holding gains (losses) during period, net of reclassification adjustment									(1,524,850)
Unrealized holding gains (losses) during period attributable to noncontrolling interests									0
Foreign currency translation adjustments	(56,720)									(56,720)
Foreign currency translation adjustments attributable to noncontrolling interests										0
Shares repurchased for treasury	(585,823)										(616,825)
Balance at end of year at Dec. 31, 2022	12,910,073	$ 830,000	$ 654	$ 2,211,444	$ 15,892,065			$ (1,646,170)	$ (1,511,364)	$ (134,806)	$ (4,377,920)
Non-redeemable noncontrolling interests	0
Total shareholders' equity	$ 12,910,073