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			(311)
Restricted stock units expensed			10,694
Stock issued to directors			535						597
Net income before noncontrolling interests	231,725			232,572						(847)
Dividends				(25,814)
Change in unrealized investment gains, net of taxes	(189,250)				(189,594)
Unrealized gains on other-than-temporarily impaired securities					339
Change in unrealized currency translation adjustments	(69,779)					(69,779)
Change in net pension asset, net of taxes	3,628						3,628
Stock exercised/vested									882
Stock repurchased									(31,362)
Stock issued to directors			535						597
Contributions										(1,356)
Other comprehensive income (loss)	(255,401)					(69,779)	3,628	(255,401)		5
End of period at Jun. 30, 2013			956,084	5,024,565	328,403	(106,455)	(11,723)	210,225	(1,999,294)	27,051
Beginning and end of period at Mar. 31, 2013
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income before noncontrolling interests	115,127
Change in unrealized investment gains, net of taxes	(197,060)
Change in unrealized currency translation adjustments	(23,156)
Change in net pension asset, net of taxes	1,814
Other comprehensive income (loss)	(218,402)					(23,156)	1,814	(218,402)
End of period at Jun. 30, 2013						(106,455)	(11,723)	210,225
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			(5,692)
Restricted stock units expensed			12,455
Stock issued to directors			591						594
Net income before noncontrolling interests	349,861			349,634						227
Dividends				(26,825)
Change in unrealized investment gains, net of taxes	121,144				120,618
Unrealized gains on other-than-temporarily impaired securities					489
Change in unrealized currency translation adjustments	20,790					20,790
Change in net pension asset, net of taxes	2,611						2,611
Stock exercised/vested									5,667
Stock repurchased									(197,254)
Stock issued to directors			591						594
Contributions										1,222
Other comprehensive income (loss)	144,545					20,790	2,611	144,545		37
End of period at Jun. 30, 2014	4,654,558		974,794	5,587,824	377,673	(39,734)	(4,040)	333,899	(2,323,828)	34,845
Beginning and end of period at Mar. 31, 2014
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income before noncontrolling interests	180,177
Change in unrealized investment gains, net of taxes	48,200
Change in unrealized currency translation adjustments	24,815
Change in net pension asset, net of taxes	2,020
Other comprehensive income (loss)	75,035					24,815	2,020	75,035
End of period at Jun. 30, 2014	$ 4,654,558					$ (39,734)	$ (4,040)	$ 333,899