CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (UNAUDITED) - USD ($) $ in Thousands		Total	Preferred shares	Common shares (par value)	Additional paid-in capital	Accumulated other comprehensive income (loss)	Unrealized gains (losses) on available for sale investments, net of tax:	Cumulative foreign currency translation adjustments, net of tax:	Retained earnings	Treasury shares, at cost
Balance at beginning of period at Dec. 31, 2023			$ 550,000	$ 2,206	$ 2,383,030	$ (365,836)	$ (347,659)	$ (18,177)	$ 6,440,528	$ (3,746,732)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Treasury shares reissued					(26,312)					28,556
Share-based compensation expense					11,426
Unrealized gains (losses) arising during the period, net of reclassification adjustment		$ (37,062)					(37,062)
Foreign currency translation adjustment		(8,951)						(8,951)
Net income		395,459							395,459
Preferred share dividends	[1]								(7,563)
Common share dividends	[1]								(37,866)
Shares repurchased										(75,728)
Balance at end of period at Mar. 31, 2024		5,505,155	550,000	2,206	2,368,144	(411,849)	(384,721)	(27,128)	6,790,558	(3,793,904)
Balance at beginning of period at Dec. 31, 2024		6,089,379	550,000	2,206	2,394,063	(267,557)	(225,617)	(41,940)	7,341,569	(3,930,902)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Treasury shares reissued					(29,059)					31,089
Share-based compensation expense					9,800
Unrealized gains (losses) arising during the period, net of reclassification adjustment		115,337					115,337
Foreign currency translation adjustment		(156)						(156)
Net income		194,071							194,071
Preferred share dividends	[1]								(7,563)
Common share dividends	[1]								(35,593)
Shares repurchased										(464,506)
Balance at end of period at Mar. 31, 2025		$ 5,902,799	$ 550,000	$ 2,206	$ 2,374,804	$ (152,376)	$ (110,280)	$ (42,096)	$ 7,492,484	$ (4,364,319)

[1] Refer to Note 9 'Shareholders' Equity' for details on dividends declared and paid related to the Company's common and preferred shares.