Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common stocks	Additional Paid In Capital	Retained earnings	Accumulated Other Comprehensive (Loss) Income	Unrealized investment (losses) gains	Currency translation adjustments	Treasury Stock	Noncontrolling Interests
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect adjustment resulting from changes in accounting principles				$ 0		$ 0
Beginning of period at Dec. 31, 2016		$ 70,535	$ 1,013,935	6,595,987		427,154	$ (371,586)	$ (2,688,817)	$ 33,926
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Restricted stock units issued			(27,959)
Restricted stock units expensed			38,796
Unrealized gains (losses) on securities not other-than-temporarily impaired	$ (51,752)					(52,628)
Unrealized gains (losses) on other-than-temporarily impaired securities						895
Net change in period	64,706						64,706
Stock exercised/vested								26,511
Stock issued								727
Stock repurchased								(47,807)
(Distributions) contributions									1,631
Net income	553,337			549,094					4,243
Dividends ($1.68, $1.39, and $1.03 per share, respectively)				(188,199)
Other comprehensive income (loss), net of tax	12,954								19
End of period at Dec. 31, 2017		70,535	1,024,772	6,956,882	$ 68,541	375,421	(306,880)	(2,709,386)	39,819
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect adjustment resulting from changes in accounting principles				215,939		(214,539)
Restricted stock units issued			(19,547)
Restricted stock units expensed			34,408
Unrealized gains (losses) on securities not other-than-temporarily impaired	(252,327)					(252,241)
Unrealized gains (losses) on other-than-temporarily impaired securities						(132)
Net change in period	(112,099)						(112,099)
Stock exercised/vested								12,981
Stock issued								689
Stock repurchased								(24,750)
(Distributions) contributions									(6,143)
Net income	649,066			640,749					8,317
Dividends ($1.68, $1.39, and $1.03 per share, respectively)				(254,951)
Other comprehensive income (loss), net of tax	(364,426)				(364,426)		(112,099)		(46)
End of period at Dec. 31, 2018	5,479,798	$ 70,535	1,039,633	7,558,619	(510,470)	(91,491)	(418,979)	(2,720,466)	41,947
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect adjustment resulting from changes in accounting principles				0		0
Restricted stock units issued			(32,370)
Restricted stock units expensed			48,779
Unrealized gains (losses) on securities not other-than-temporarily impaired	215,902					215,636
Unrealized gains (losses) on other-than-temporarily impaired securities						369
Net change in period	37,166						37,166
Stock exercised/vested								11,431
Stock issued								549
Stock repurchased								(18,225)
(Distributions) contributions									(688)
Net income	683,985			681,944					2,041
Dividends ($1.68, $1.39, and $1.03 per share, respectively)				(308,191)
Other comprehensive income (loss), net of tax	253,068				253,068		37,166		103
End of period at Dec. 31, 2019	$ 6,118,342		$ 1,056,042	$ 7,932,372	$ (257,299)	$ 124,514	$ (381,813)	$ (2,726,711)	$ 43,403