Unaudited Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Thousands	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, 2020		$ 780,000	$ 643	$ 1,977,794	$ 12,362,463	$ 488,895	$ 501,295	$ (12,400)	$ (2,503,909)
Preferred shares issued		500,000
Common shares issued, net			4
Amortization of share-based compensation				57,063
Issue costs on preferred shares				(14,179)
Other changes				8,241
Net income (loss)	$ 1,194,372				1,194,372
Net (income) loss attributable to noncontrolling interests	(80,730)				(80,730)
Preferred share dividends	(22,069)				(22,069)
Unrealized holding gains (losses) during period, net of reclassification adjustment							(241,029)
Unrealized holding gains (losses) during period attributable to noncontrolling interests							4,436
Foreign currency translation adjustments	(22,379)							(22,379)
Foreign currency translation adjustments attributable to noncontrolling interests								125
Shares repurchased for treasury									(503,669)
Balance at end of period at Jun. 30, 2021	13,986,072	1,280,000	647	2,028,919	13,454,036	230,048	264,702	(34,654)	(3,007,578)
Non-redeemable noncontrolling interests, end of period at Jun. 30, 2021	918,874
Total shareholders’ equity at Jun. 30, 2021	14,904,946
Balance at beginning of period at Mar. 31, 2021		780,000	645	2,014,741	12,790,216	205,827	246,711	(40,884)	(2,694,957)
Preferred shares issued		500,000
Common shares issued, net			2
Amortization of share-based compensation				16,490
Issue costs on preferred shares				(14,179)
Other changes				11,867
Net income (loss)	718,664				718,664
Net (income) loss attributable to noncontrolling interests	(43,178)				(43,178)
Preferred share dividends	(11,666)				(11,666)
Unrealized holding gains (losses) during period, net of reclassification adjustment							18,024
Unrealized holding gains (losses) during period attributable to noncontrolling interests							(33)
Foreign currency translation adjustments	6,205							6,205
Foreign currency translation adjustments attributable to noncontrolling interests								25
Shares repurchased for treasury									(312,621)
Balance at end of period at Jun. 30, 2021	13,986,072	1,280,000	647	2,028,919	13,454,036	230,048	264,702	(34,654)	(3,007,578)
Non-redeemable noncontrolling interests, end of period at Jun. 30, 2021	918,874
Total shareholders’ equity at Jun. 30, 2021	14,904,946
Balance at beginning of period at Dec. 31, 2021	13,545,896	830,000	648	2,085,075	14,455,868	(64,600)	13,486	(78,086)	(3,761,095)
Preferred shares issued		0
Common shares issued, net			4
Amortization of share-based compensation				66,505
Issue costs on preferred shares				0
Other changes				19,081
Net income (loss)	601,377				601,377
Net (income) loss attributable to noncontrolling interests	(1,233)				(1,233)
Preferred share dividends	(20,368)				(20,368)
Unrealized holding gains (losses) during period, net of reclassification adjustment							(1,122,372)
Unrealized holding gains (losses) during period attributable to noncontrolling interests							0
Foreign currency translation adjustments	(71,293)							(71,293)
Foreign currency translation adjustments attributable to noncontrolling interests								0
Shares repurchased for treasury									(600,031)
Balance at end of period at Jun. 30, 2022	12,417,566	830,000	652	2,170,661	15,035,644	(1,258,265)	(1,108,886)	(149,379)	(4,361,126)
Non-redeemable noncontrolling interests, end of period at Jun. 30, 2022	0
Total shareholders’ equity at Jun. 30, 2022	12,417,566
Balance at beginning of period at Mar. 31, 2022		830,000	651	2,134,241	14,641,484	(649,445)	(568,591)	(80,854)	(4,037,342)
Preferred shares issued		0
Common shares issued, net			1
Amortization of share-based compensation				21,137
Issue costs on preferred shares				0
Other changes				15,283
Net income (loss)	403,945				403,945
Net (income) loss attributable to noncontrolling interests	399				399
Preferred share dividends	(10,184)				(10,184)
Unrealized holding gains (losses) during period, net of reclassification adjustment							(540,295)
Unrealized holding gains (losses) during period attributable to noncontrolling interests							0
Foreign currency translation adjustments	(68,525)							(68,525)
Foreign currency translation adjustments attributable to noncontrolling interests								0
Shares repurchased for treasury									(323,784)
Balance at end of period at Jun. 30, 2022	12,417,566	$ 830,000	$ 652	$ 2,170,661	$ 15,035,644	$ (1,258,265)	$ (1,108,886)	$ (149,379)	$ (4,361,126)
Non-redeemable noncontrolling interests, end of period at Jun. 30, 2022	0
Total shareholders’ equity at Jun. 30, 2022	$ 12,417,566