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, 2013		$ 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]
Restricted stock units issued, net of tax			(3,338)
Stock units expensed			6,203
Net income before noncontrolling interests	169,684			169,673						11
Dividends				(12,775)
Change in unrealized investment gains (loss), net of taxes	72,944				72,563
Unrealized gains on other-than-temporarily impaired securities					363
Change in unrealized currency translation adjustments	(4,025)					(4,025)
Change in net pension asset, net of taxes	591						591
Stock exercised/vested									3,322
Stock repurchased									(192,668)
Contributions										1,526
Other comprehensive income (loss)	69,510					(4,025)	591	69,510		18
End of period at Mar. 31, 2014			970,305	5,421,913	329,492	(64,549)	(6,060)	258,883	(2,322,181)	34,914
Beginning and end of period at Dec. 31, 2014	4,624,134	47,024	991,512	5,732,410	306,199	(122,649)	0		(2,364,551)	34,189
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Restricted stock units issued, net of tax			(1,678)
Stock units expensed			8,171
Net income before noncontrolling interests	118,444			118,307						137
Dividends				(13,749)
Change in unrealized investment gains (loss), net of taxes	16,291				16,308
Unrealized gains on other-than-temporarily impaired securities					5
Change in unrealized currency translation adjustments	(47,805)					(47,805)
Change in net pension asset, net of taxes	0						0
Stock exercised/vested									331
Stock repurchased									(91,213)
Contributions										111
Other comprehensive income (loss)	(31,514)					(47,805)	0	(31,514)		(22)
End of period at Mar. 31, 2015	$ 4,613,037		$ 998,005	$ 5,836,968	$ 322,512	$ (170,454)	$ 0	$ 152,058	$ (2,455,433)	$ 34,415