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 gain	Currency Translation Adjustments	Treasury stock	Noncontrolling interest
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect adjustment resulting from changes in accounting principles		$ 105,803	$ 981,104	$ 9,015,135	$ (281,955)	$ 90,900	$ (372,855)	$ (3,167,076)	$ 14,719
Beginning of period at Dec. 31, 2021		105,803	981,104	9,015,135	(281,955)	90,900	(372,855)	(3,167,076)	14,719
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Restricted stock units issued			(30,751)
Restricted stock units expensed			34,450
Net income before noncontrolling interests	$ 1,002,970			998,839					4,131
Dividends ($0.61, $0.10, $1.32 and $0.79 per share, respectively)				(208,737)
Change in unrealized (losses) gains on securities without an allowance for expected credit losses	(1,076,217)					(1,055,628)
Change in unrealized (losses) gains on securities with an allowance for expected credit losses						(20,590)
Net change in period	(27,637)						(27,637)
Stock exercised/vested								9,679
Stock repurchased								(6,570)
Other	0
(Distributions) contributions									5,061
Other comprehensive loss, net of tax	$ (1,103,854)				(1,103,854)		(27,637)		(1)
End of period at Sep. 30, 2022			984,803	9,805,237	(1,385,810)	(985,318)	(400,492)	(3,163,967)	23,910
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock dividends, per share, cash paid (in dollars per share)	$ 0.79
Cumulative effect adjustment resulting from changes in accounting principles		105,803	1,001,093	9,602,948	(1,029,630)	(669,654)	(359,976)	(3,165,729)	22,388
Beginning of period at Jun. 30, 2022		105,803	1,001,093	9,602,948	(1,029,630)	(669,654)	(359,976)	(3,165,729)	22,388
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Restricted stock units issued			(28,381)
Restricted stock units expensed			12,091
Net income before noncontrolling interests	$ 230,474			228,879					1,595
Dividends ($0.61, $0.10, $1.32 and $0.79 per share, respectively)				(26,590)
Change in unrealized (losses) gains on securities without an allowance for expected credit losses	(315,664)					(311,659)
Change in unrealized (losses) gains on securities with an allowance for expected credit losses						(4,005)
Net change in period	(40,516)						(40,516)
Stock exercised/vested								8,332
Stock repurchased								(6,570)
Other	0
(Distributions) contributions									(73)
Other comprehensive loss, net of tax	$ (356,180)				(356,180)		(40,516)		0
End of period at Sep. 30, 2022			984,803	9,805,237	(1,385,810)	(985,318)	(400,492)	(3,163,967)	23,910
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock dividends, per share, cash paid (in dollars per share)	$ 0.10
Cumulative effect adjustment resulting from changes in accounting principles			984,803	9,805,237	(1,385,810)	(985,318)	(400,492)	(3,163,967)	23,910
Cumulative effect adjustment resulting from changes in accounting principles	$ 6,768,161	105,803	997,534	10,161,005	(1,264,581)	(892,905)	(371,676)	(3,251,429)	19,829
Beginning of period at Dec. 31, 2022	6,768,161	105,803	997,534	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 ($0.61, $0.10, $1.32 and $0.79 per share, respectively)				(344,328)
Change in unrealized (losses) gains on securities without an allowance for expected credit losses	(50,850)					(47,757)
Change in unrealized (losses) gains 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)
(Distributions) contributions									(6,361)
Other comprehensive loss, net of tax	(58,237)				(58,237)		(7,387)		(1)
End of period at Sep. 30, 2023	$ 6,929,909		1,008,301	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)	$ 1.32
Cumulative effect adjustment resulting from changes in accounting principles		105,803	1,020,818	10,624,518	(1,181,673)	(825,391)	(356,282)	(3,682,281)	21,167
Beginning of period at Jun. 30, 2023		$ 105,803	1,020,818	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 ($0.61, $0.10, $1.32 and $0.79 per share, respectively)				(157,407)
Change in unrealized (losses) gains on securities without an allowance for expected credit losses	(118,365)					(108,121)
Change in unrealized (losses) gains 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
(Distributions) contributions									(6,681)
Other comprehensive loss, net of tax	(141,146)				(141,146)		(22,781)		0
End of period at Sep. 30, 2023	$ 6,929,909		1,008,301	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)	$ 0.61
Cumulative effect adjustment resulting from changes in accounting principles	$ 6,929,909		$ 1,008,301	$ 10,800,697	$ (1,322,819)	$ (943,756)	$ (379,063)	$ (3,676,403)	$ 14,330