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	Cumulative effect adjustment resulting from changes in accounting principles Retained earnings	Cumulative effect adjustment resulting from changes in accounting principles Accumulated Other Comprehensive Income (Loss)	Cumulative effect adjustment resulting from changes in accounting principles Unrealized investment gain	Cumulative effect adjustment resulting from changes in accounting principles Currency Translation Adjustments
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect adjustment resulting from changes in accounting principles		$ 70,535	$ 1,056,042	$ 7,932,372	$ (257,299)	$ 124,514	$ (381,813)	$ (2,726,711)	$ 43,403	$ (30,514)	$ 24,952	$ 24,952	$ 0
Beginning of period at Dec. 31, 2019		70,535	1,056,042	7,932,372	(257,299)	124,514	(381,813)	(2,726,711)	43,403	(30,514)	$ 24,952	24,952	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Restricted stock units issued			(26,773)
Restricted stock units expensed			35,450
Net income before noncontrolling interests	$ 220,495			218,520					1,975
Dividends ( $0.13, $0.12, $0.88 and $0.35 per share, respectively)				(62,822)
Change in unrealized (losses) gains on securities without an allowance for expected credit losses	98,016					77,537
Change in unrealized gains on securities with an allowance for expected credit losses						20,477
Net change in period	(36,553)						(36,553)
Stock exercised/vested								11,758
Stock repurchased								(311,859)
Distributions									(816)
Other comprehensive income (loss), net of tax	$ 61,463				61,463		(36,553)		(2)
End of period at Sep. 30, 2020			1,064,719	8,057,556	(170,886)	247,480	(418,366)	(3,026,812)	44,560
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock dividends, per share, cash paid (in dollars per share)	$ 0.35
Cumulative effect adjustment resulting from changes in accounting principles		70,535	1,076,043	7,927,280	(249,350)	209,210	(458,560)	(3,023,392)	44,275	0		0
Beginning of period at Jun. 30, 2020		70,535	1,076,043	7,927,280	(249,350)	209,210	(458,560)	(3,023,392)	44,275	0		0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Restricted stock units issued			(23,387)
Restricted stock units expensed			12,063
Net income before noncontrolling interests	$ 152,366			151,678					688
Dividends ( $0.13, $0.12, $0.88 and $0.35 per share, respectively)				(21,402)
Change in unrealized (losses) gains on securities without an allowance for expected credit losses	38,273					35,111
Change in unrealized gains on securities with an allowance for expected credit losses						3,159
Net change in period	40,194						40,194
Stock exercised/vested								9,537
Stock repurchased								(12,957)
Distributions									(400)
Other comprehensive income (loss), net of tax	$ 78,467				78,467		40,194		(3)
End of period at Sep. 30, 2020			1,064,719	8,057,556	(170,886)	247,480	(418,366)	(3,026,812)	44,560
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock dividends, per share, cash paid (in dollars per share)	$ 0.12
Cumulative effect adjustment resulting from changes in accounting principles			1,064,719	8,057,556	(170,886)	247,480	(418,366)	(3,026,812)	44,560
Cumulative effect adjustment resulting from changes in accounting principles	$ 6,325,797	70,535	1,012,482	8,348,381	(62,172)	289,714	(351,886)	(3,058,425)	14,995	0		0
Beginning of period at Dec. 31, 2020	6,325,797	70,535	1,012,482	8,348,381	(62,172)	289,714	(351,886)	(3,058,425)	14,995	0		0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Restricted stock units issued			(28,668)
Restricted stock units expensed			34,486
Net income before noncontrolling interests	736,712			728,060					8,652
Dividends ( $0.13, $0.12, $0.88 and $0.35 per share, respectively)				(156,107)
Change in unrealized (losses) gains on securities without an allowance for expected credit losses	(102,454)					(112,852)
Change in unrealized gains on securities with an allowance for expected credit losses						10,397
Net change in period	(26,235)						(26,235)
Stock exercised/vested								10,985
Stock repurchased								(122,426)
Distributions									(8,376)
Other comprehensive income (loss), net of tax	(128,689)				(128,689)		(26,235)		(1)
End of period at Sep. 30, 2021	$ 6,663,711		1,018,300	8,920,334	(190,862)	187,259	(378,121)	(3,169,866)	15,270
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		70,535	1,035,166	8,682,088	(122,444)	222,855	(345,299)	(3,087,069)	9,678	0		0
Beginning of period at Jun. 30, 2021		$ 70,535	1,035,166	8,682,088	(122,444)	222,855	(345,299)	(3,087,069)	9,678	$ 0		$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Restricted stock units issued			(28,741)
Restricted stock units expensed			11,875
Net income before noncontrolling interests	$ 267,318			261,297					6,021
Dividends ( $0.13, $0.12, $0.88 and $0.35 per share, respectively)				(23,051)
Change in unrealized (losses) gains on securities without an allowance for expected credit losses	(35,596)					(35,707)
Change in unrealized gains on securities with an allowance for expected credit losses						111
Net change in period	(32,822)						(32,822)
Stock exercised/vested								9,946
Stock repurchased								(92,743)
Distributions									(429)
Other comprehensive income (loss), net of tax	(68,418)				(68,418)		(32,822)		0
End of period at Sep. 30, 2021	$ 6,663,711		1,018,300	8,920,334	(190,862)	187,259	(378,121)	(3,169,866)	15,270
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock dividends, per share, cash paid (in dollars per share)	$ 0.13
Cumulative effect adjustment resulting from changes in accounting principles	$ 6,663,711		$ 1,018,300	$ 8,920,334	$ (190,862)	$ 187,259	$ (378,121)	$ (3,169,866)	$ 15,270