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	$ 1,039,633	$ 7,558,619	$ (510,470)	$ (91,491)	$ (418,979)	$ (2,720,466)	$ 41,947	$ 0		$ 0
Beginning of period at Dec. 31, 2018		70,535	1,039,633	7,558,619	(510,470)	(91,491)	(418,979)	(2,720,466)	41,947	0		0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Restricted stock units issued			(30,659)
Restricted stock units expensed			36,474
Cumulative effect adjustment resulting from changes in accounting principles		70,535	1,045,448	7,971,019	(322,100)	128,293	(450,393)	(2,708,606)	43,147	0		0
Net income before noncontrolling interests	$ 564,192			562,638					1,554
Dividends ($0.12, $0.11, $0.35 and $0.82 per share, respectively)				(150,238)
Change in unrealized gains (losses) on securities without an allowance for expected credit losses	219,679					219,388
Change in unrealized gains on securities with an allowance for expected credit losses						396
Net change in period	(31,414)						(31,414)
Stock exercised/vested								11,860
Stock repurchased								0
Distributions									(459)
Other comprehensive (loss) income, net of tax	$ 188,265				188,265		(31,414)		105
End of period at Sep. 30, 2019			1,045,448	7,971,019	(322,100)	128,293	(450,393)	(2,708,606)	43,147
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock dividends, per share, cash paid (in dollars per share)	$ 0.82
Cumulative effect adjustment resulting from changes in accounting principles		70,535	1,058,416	7,826,015	(260,796)	152,915	(413,711)	(2,717,410)	43,318	0		0
Beginning of period at Jun. 30, 2019		70,535	1,058,416	7,826,015	(260,796)	152,915	(413,711)	(2,717,410)	43,318	0		0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Restricted stock units issued			(28,155)
Restricted stock units expensed			15,187
Cumulative effect adjustment resulting from changes in accounting principles		70,535	1,045,448	7,971,019	(322,100)	128,293	(413,711)	(2,708,606)	43,147	0		0
Net income before noncontrolling interests	$ 165,151			165,208					(57)
Dividends ($0.12, $0.11, $0.35 and $0.82 per share, respectively)				(20,204)
Change in unrealized gains (losses) on securities without an allowance for expected credit losses	(24,745)					(25,005)
Change in unrealized gains on securities with an allowance for expected credit losses						383
Net change in period	(36,682)						(36,682)
Stock exercised/vested								8,804
Stock repurchased								0
Distributions									(237)
Other comprehensive (loss) income, net of tax	$ (61,427)				(61,427)		(36,682)		123
End of period at Sep. 30, 2019			1,045,448	7,971,019	(322,100)	128,293	(450,393)	(2,708,606)	43,147
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock dividends, per share, cash paid (in dollars per share)	$ 0.11
Cumulative effect adjustment resulting from changes in accounting principles			1,045,448	7,971,019	(322,100)	128,293	(450,393)	(2,708,606)	43,147
Cumulative effect adjustment resulting from changes in accounting principles	$ 6,118,342	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	6,118,342	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
Cumulative effect adjustment resulting from changes in accounting principles	6,118,342	70,535	1,064,719	8,057,556	(170,886)	247,480	(418,366)	(3,026,812)	44,560	(30,514)	$ 24,952	24,952	$ 0
Net income before noncontrolling interests	220,495			218,520					1,975
Dividends ($0.12, $0.11, $0.35 and $0.82 per share, respectively)				(62,822)
Change in unrealized gains (losses) 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 (loss) income, net of tax	61,463				61,463		(36,553)		(2)
End of period at Sep. 30, 2020	$ 6,039,672		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
Cumulative effect adjustment resulting from changes in accounting principles	$ 6,039,672	$ 70,535	1,064,719	8,057,556	(170,886)	247,480	(418,366)	(3,026,812)	44,560	$ 0		$ 0
Net income before noncontrolling interests	152,366			151,678					688
Dividends ($0.12, $0.11, $0.35 and $0.82 per share, respectively)				(21,402)
Change in unrealized gains (losses) 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 (loss) income, net of tax	78,467				78,467		40,194		(3)
End of period at Sep. 30, 2020	$ 6,039,672		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	$ 6,039,672		$ 1,064,719	$ 8,057,556	$ (170,886)	$ 247,480	$ (418,366)	$ (3,026,812)	$ 44,560