Consolidated Statements of Stockholders' Equity Statement (USD $) In Thousands, unless otherwise specified	Total	Common stocks	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]	Accumulated Translation Adjustment [Member]	Accumulated Defined Benefit Plans Adjustment [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Stock [Member]	Noncontrolling Interest [Member]
Beginning and end of period at Dec. 31, 2012		$ 47,024	$ 945,166	$ 4,817,807	$ 517,658	$ (36,676)	$ (15,351)		$ (1,969,411)	$ 29,249
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Options exercised and restricted stock units issued, net of tax			(1,428)
Restricted stock units expensed			17,031
Stock issued to directors			535						597
Net income before noncontrolling interests	369,913			369,546						367
Dividends				(39,336)
Change in unrealized investment gains (losses), net of taxes	(228,129)				(228,677)
Unrealized gains on other-than-temporarily impaired securities					534
Change in unrealized currency translation adjustments	(25,451)					(25,451)
Change in net pension asset, net of taxes	5,442						5,442
Stock exercised/vested									1,434
Stock repurchased									(39,370)
Stock issued to directors			535						597
Contributions										(1,406)
Other comprehensive income (loss)	(248,138)					(25,451)	5,442	(248,138)		14
End of period at Sep. 30, 2013			961,304	5,148,017	289,515	(62,127)	(9,909)	217,479	(2,006,750)	28,224
Beginning and end of period at Jun. 30, 2013
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income before noncontrolling interests	138,188
Change in unrealized investment gains (losses), net of taxes	(38,879)
Change in unrealized currency translation adjustments	44,328
Change in net pension asset, net of taxes	1,814
Other comprehensive income (loss)	7,263					44,328	1,814	7,263
End of period at Sep. 30, 2013						(62,127)	(9,909)	217,479
Beginning and end of period at Dec. 31, 2013	4,369,394	47,024	967,440	5,265,015	256,566	(60,524)	(6,651)		(2,132,835)	33,359
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Options exercised and restricted stock units issued, net of tax			(6,383)
Restricted stock units expensed			20,456
Stock issued to directors			591						594
Net income before noncontrolling interests	538,652			538,173						479
Dividends				(40,782)
Change in unrealized investment gains (losses), net of taxes	108,232				107,501
Unrealized gains on other-than-temporarily impaired securities					612
Change in unrealized currency translation adjustments	(28,590)					(28,590)
Change in net pension asset, net of taxes	4,631						4,631
Stock exercised/vested									6,384
Stock repurchased									(230,319)
Stock issued to directors			591						594
Contributions										614
Other comprehensive income (loss)	84,273					(28,590)	4,631	84,273		119
End of period at Sep. 30, 2014	4,743,474		982,104	5,762,406	364,679	(89,114)	(2,020)	273,545	(2,356,176)	34,571
Beginning and end of period at Jun. 30, 2014
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income before noncontrolling interests	188,791
Change in unrealized investment gains (losses), net of taxes	(12,912)
Change in unrealized currency translation adjustments	(49,380)
Change in net pension asset, net of taxes	2,020
Other comprehensive income (loss)	(60,272)					(49,380)	2,020	(60,272)
End of period at Sep. 30, 2014	$ 4,743,474					$ (89,114)	$ (2,020)	$ 273,545