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			(2,504)
Restricted stock units expensed			21,287
Cumulative effect adjustment resulting from changes in accounting principles		70,535	1,058,416	7,826,015	(510,470)	152,915	(413,711)	(2,717,410)	43,318	0		0
Net income before noncontrolling interests	$ 399,041			397,431					1,610
Dividends ($0.12, $0.61, $0.23 and $0.71 per share, respectively)				(130,035)
Change in unrealized gains on securities without an allowance for expected credit losses	244,424					244,393
Change in unrealized gains on securities with an allowance for expected credit losses						13
Net change in period	5,268						5,268
Stock exercised/vested								3,056
Stock repurchased								0
Distributions									(221)
Other comprehensive (loss) income, net of tax	$ 249,692				249,692		5,268		(18)
End of period at Jun. 30, 2019			1,058,416	7,826,015	(260,796)	152,915	(413,711)	(2,717,410)	43,318
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock dividends, per share, cash paid (in dollars per share)	$ 0.71
Cumulative effect adjustment resulting from changes in accounting principles		70,535	1,053,372	7,721,039	(364,983)	34,236	(399,219)	(2,720,011)	42,844	0		0
Beginning of period at Mar. 31, 2019		70,535	1,053,372	7,721,039	(364,983)	34,236	(399,219)	(2,720,011)	42,844	0		0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Restricted stock units issued			(2,049)
Restricted stock units expensed			7,093
Cumulative effect adjustment resulting from changes in accounting principles		70,535	1,058,416	7,826,015	(364,983)	152,915	(413,711)	(2,717,410)	43,318	0		0
Net income before noncontrolling interests	$ 217,427			216,709					718
Dividends ($0.12, $0.61, $0.23 and $0.71 per share, respectively)				(111,733)
Change in unrealized gains on securities without an allowance for expected credit losses	118,649					118,597
Change in unrealized gains on securities with an allowance for expected credit losses						82
Net change in period	(14,492)						(14,492)
Stock exercised/vested								2,601
Stock repurchased								0
Distributions									(274)
Other comprehensive (loss) income, net of tax	$ 104,157				104,157		(14,492)		30
End of period at Jun. 30, 2019			1,058,416	7,826,015	(260,796)	152,915	(413,711)	(2,717,410)	43,318
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			1,058,416	7,826,015	(260,796)	152,915	(413,711)	(2,717,410)	43,318
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			(3,386)
Restricted stock units expensed			23,387
Cumulative effect adjustment resulting from changes in accounting principles	6,118,342	70,535	1,076,043	7,927,280	(257,299)	209,210	(458,560)	(3,023,392)	44,275	(30,514)	$ 24,952	24,952	$ 0
Net income before noncontrolling interests	68,130			66,842					1,288
Dividends ($0.12, $0.61, $0.23 and $0.71 per share, respectively)				(41,420)
Change in unrealized gains on securities without an allowance for expected credit losses	59,743					34,753
Change in unrealized gains on securities with an allowance for expected credit losses						24,991
Net change in period	(76,747)						(76,747)
Stock exercised/vested								2,221
Stock repurchased								(298,902)
Distributions									(417)
Other comprehensive (loss) income, net of tax	(17,004)				(17,004)		(76,747)		1
End of period at Jun. 30, 2020	$ 5,845,391		1,076,043	7,927,280	(249,350)	209,210	(458,560)	(3,023,392)	44,275
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock dividends, per share, cash paid (in dollars per share)	$ 0.23
Cumulative effect adjustment resulting from changes in accounting principles		70,535	1,063,084	7,877,371	(589,521)	(109,514)	(480,007)	(2,927,994)	44,069	0		0
Beginning of period at Mar. 31, 2020		70,535	1,063,084	7,877,371	(589,521)	(109,514)	(480,007)	(2,927,994)	44,069	0		0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Restricted stock units issued			1,204
Restricted stock units expensed			11,755
Cumulative effect adjustment resulting from changes in accounting principles	$ 5,845,391	$ 70,535	1,076,043	7,927,280	(589,521)	209,210	(458,560)	(3,023,392)	44,275	$ 0		$ 0
Net income before noncontrolling interests	71,656			71,260					396
Dividends ($0.12, $0.61, $0.23 and $0.71 per share, respectively)				(21,351)
Change in unrealized gains on securities without an allowance for expected credit losses	318,725					295,274
Change in unrealized gains on securities with an allowance for expected credit losses						23,450
Net change in period	21,447						21,447
Stock exercised/vested								883
Stock repurchased								(96,281)
Distributions									(189)
Other comprehensive (loss) income, net of tax	340,172				340,172		21,447		(1)
End of period at Jun. 30, 2020	$ 5,845,391		1,076,043	7,927,280	(249,350)	209,210	(458,560)	(3,023,392)	44,275
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	$ 5,845,391		$ 1,076,043	$ 7,927,280	$ (249,350)	$ 209,210	$ (458,560)	$ (3,023,392)	$ 44,275