CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS’ EQUITY - USD ($) $ in Thousands		Total	Preferred stocks	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 year at Dec. 31, 2019			$ 775,000	$ 2,206	$ 2,317,212	$ 171,710	$ 181,521	$ (9,811)	$ 6,056,686	$ (3,778,806)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares repurchased			(225,000)
Treasury shares reissued					(22,732)					24,620
Share-based compensation expense					35,574
Unrealized gains (losses) arising during the year, net of reclassification adjustment		$ 239,114					239,114
Foreign currency translation adjustment		3,571						3,571
Net income (loss)		(120,424)							(120,424)
Preferred share dividends	[1]								(30,250)
Common share dividends	[1]								(142,405)
Shares repurchased										(10,382)
Stockholders' Equity Attributable to Parent, Ending Balance at Dec. 31, 2020		5,295,694	550,000	2,206	2,330,054	414,395	420,635	(6,240)	5,763,607	(3,764,568)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Treasury shares reissued					(24,655)					25,800
Share-based compensation expense					40,780
Unrealized gains (losses) arising during the year, net of reclassification adjustment		(358,480)					(358,480)
Foreign currency translation adjustment		621						621
Net income (loss)		618,609							618,609
Preferred share dividends	[1]								(30,250)
Common share dividends	[1]								(147,221)
Shares repurchased										(10,242)
Stockholders' Equity Attributable to Parent, Ending Balance at Dec. 31, 2021		5,410,656	550,000	2,206	2,346,179	56,536	62,155	(5,619)	6,204,745	(3,749,010)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Treasury shares reissued					(31,175)					32,720
Share-based compensation expense					51,249
Unrealized gains (losses) arising during the year, net of reclassification adjustment		(805,850)					(805,850)
Foreign currency translation adjustment		(10,986)						(10,986)
Net income (loss)		223,083							223,083
Preferred share dividends	[1]								(30,250)
Common share dividends	[1]								(150,556)
Shares repurchased										(48,981)
Stockholders' Equity Attributable to Parent, Ending Balance at Dec. 31, 2022		$ 4,639,910	$ 550,000	$ 2,206	$ 2,366,253	$ (760,300)	$ (743,695)	$ (16,605)	$ 6,247,022	$ (3,765,271)

[1] Refer to Note 15 'Shareholders' Equity' for details on dividends declared and paid related to the Company's common and preferred shares.