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
Beginning of period at Dec. 31, 2015		$ 47,024	$ 1,005,455	$ 6,178,070		$ 180,695	$ (247,393)	$ (2,563,605)	$ 32,962
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Restricted stock units issued			(3,421)
Restricted stock units expensed			25,431
Net income before noncontrolling interests	$ 449,816			449,127					689
Dividends				(107,661)
Unrealized gains on securities not other-than-temporarily impaired	134,213					133,866
Unrealized gains on other-than-temporarily impaired securities						413
Net change in period	(77,389)						(77,389)
Stock exercised/vested								5,023
Stock repurchased								(99,870)
Stock incentive plans expensed								0
Contributions									2,474
Other comprehensive loss, net of tax	56,824				$ 56,824		(77,389)		(66)
End of period at Sep. 30, 2016			1,027,465	6,519,536	(9,808)	314,974	(324,782)	(2,658,452)	36,059
Beginning of period at Dec. 31, 2016	5,081,134	$ 47,024	1,037,446	6,595,987		427,154	(371,586)	(2,688,817)	33,926
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Restricted stock units issued			(27,047)
Restricted stock units expensed			30,176
Net income before noncontrolling interests	397,065			394,505					2,560
Dividends				(110,430)
Unrealized gains on securities not other-than-temporarily impaired	26,598					25,712
Unrealized gains on other-than-temporarily impaired securities						905
Net change in period	71,574						71,574
Stock exercised/vested								25,584
Stock repurchased								(28,378)
Stock incentive plans expensed								727
Contributions									3,646
Other comprehensive loss, net of tax	98,172				98,172		71,574		(19)
End of period at Sep. 30, 2017	$ 5,470,649		$ 1,040,575	$ 6,880,062	$ 153,759	$ 453,771	$ (300,012)	$ (2,690,884)	$ 40,113