Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common stock	Additional paid-in capital	Retained earnings	Accumulated Other Comprehensive Income (Loss)	Unrealized Investment (Losses) Gains	Currency Translation Adjustments	Treasury stock	Noncontrolling interest
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect adjustment resulting from changes in accounting principles		$ 158,705	$ 944,632	$ 10,161,005	$ (1,264,581)	$ (892,905)	$ (371,676)	$ (3,251,429)	$ 19,829
Beginning of period at Dec. 31, 2022		158,705	944,632	10,161,005	(1,264,581)	(892,905)	(371,676)	(3,251,429)	19,829
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Restricted stock units issued			(25,228)
Restricted stock units expensed			35,995
Net income before noncontrolling interests	$ 984,883			984,020					863
Dividends ($0.33, $0.41, $0.81 and $0.88 per share, respectively)				(344,328)
Change in unrealized gains (losses) on securities without an allowance for expected credit losses	(50,850)					(47,757)
Change in unrealized gains (losses) on securities with an allowance for expected credit losses						(3,094)
Net change in period	(7,387)						(7,387)
Stock exercised/vested								9,461
Stock repurchased								(430,536)
Other	(3,899)
Contributions (distribution)									(6,361)
Other comprehensive income (loss), net of tax	$ (58,237)				(58,237)	(50,850)	(7,387)		(1)
End of period at Sep. 30, 2023			955,399	10,800,697	(1,322,819)	(943,756)	(379,063)	(3,676,403)	14,330
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock dividends, per share, cash paid (in dollars per share)	$ 0.88
Cumulative effect adjustment resulting from changes in accounting principles		158,705	967,916	10,624,518	(1,181,673)	(825,391)	(356,282)	(3,682,281)	21,167
Beginning of period at Jun. 30, 2023		158,705	967,916	10,624,518	(1,181,673)	(825,391)	(356,282)	(3,682,281)	21,167
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Restricted stock units issued			(25,226)
Restricted stock units expensed			12,709
Net income before noncontrolling interests	$ 333,430			333,586					(156)
Dividends ($0.33, $0.41, $0.81 and $0.88 per share, respectively)				(157,407)
Change in unrealized gains (losses) on securities without an allowance for expected credit losses	(118,365)					(108,121)
Change in unrealized gains (losses) on securities with an allowance for expected credit losses						(10,244)
Net change in period	(22,781)						(22,781)
Stock exercised/vested								8,469
Stock repurchased								(2,917)
Other	326
Contributions (distribution)									(6,681)
Other comprehensive income (loss), net of tax	$ (141,146)				(141,146)	(118,365)	(22,781)		0
End of period at Sep. 30, 2023			955,399	10,800,697	(1,322,819)	(943,756)	(379,063)	(3,676,403)	14,330
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock dividends, per share, cash paid (in dollars per share)	$ 0.41
Cumulative effect adjustment resulting from changes in accounting principles			955,399	10,800,697	(1,322,819)	(943,756)	(379,063)	(3,676,403)	14,330
Cumulative effect adjustment resulting from changes in accounting principles	$ 7,469,237	158,705	964,789	11,040,908	(925,838)	(586,354)	(339,484)	(3,783,133)	13,806
Beginning of period at Dec. 31, 2023	7,469,237	158,705	964,789	11,040,908	(925,838)	(586,354)	(339,484)	(3,783,133)	13,806
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Restricted stock units issued			(30,075)
Restricted stock units expensed			38,318
Net income before noncontrolling interests	1,179,234			1,180,014					(780)
Dividends ($0.33, $0.41, $0.81 and $0.88 per share, respectively)				(311,514)
Change in unrealized gains (losses) on securities without an allowance for expected credit losses	297,533					293,064
Change in unrealized gains (losses) on securities with an allowance for expected credit losses						4,470
Net change in period	25,160						25,160
Stock exercised/vested								9,488
Stock repurchased								(236,243)
Other	(1,849)
Contributions (distribution)									111
Other comprehensive income (loss), net of tax	322,693				322,693	297,533	25,160		1
End of period at Sep. 30, 2024	$ 8,439,402		973,032	11,909,408	(603,144)	(288,820)	(314,324)	(4,011,737)	13,138
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock dividends, per share, cash paid (in dollars per share)	$ 0.81
Cumulative effect adjustment resulting from changes in accounting principles		158,705	986,892	11,669,567	(1,033,640)	(669,813)	(363,827)	(4,007,742)	13,269
Beginning of period at Jun. 30, 2024		$ 158,705	986,892	11,669,567	(1,033,640)	(669,813)	(363,827)	(4,007,742)	13,269
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Restricted stock units issued			(26,930)
Restricted stock units expensed			13,070
Net income before noncontrolling interests	$ 365,314			365,634					(320)
Dividends ($0.33, $0.41, $0.81 and $0.88 per share, respectively)				(125,793)
Change in unrealized gains (losses) on securities without an allowance for expected credit losses	380,993					369,827
Change in unrealized gains (losses) on securities with an allowance for expected credit losses						11,166
Net change in period	49,503						49,503
Stock exercised/vested								8,164
Stock repurchased								(12,480)
Other	321
Contributions (distribution)									189
Other comprehensive income (loss), net of tax	430,496				430,496	380,993	49,503		0
End of period at Sep. 30, 2024	$ 8,439,402		973,032	11,909,408	(603,144)	(288,820)	(314,324)	(4,011,737)	13,138
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock dividends, per share, cash paid (in dollars per share)	$ 0.33
Cumulative effect adjustment resulting from changes in accounting principles	$ 8,439,402		$ 973,032	$ 11,909,408	$ (603,144)	$ (288,820)	$ (314,324)	$ (4,011,737)	$ 13,138