Consolidated Statements of Stockholders' Equity Statement - USD ($) $ in Thousands	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 Other Comprehensive Income (Loss) [Member]	Treasury Stock [Member]	Noncontrolling Interest [Member]
Beginning and end of period at Dec. 31, 2014		$ 47,024	$ 991,512	$ 5,732,410	$ 306,199	$ (122,649)		$ (2,364,551)	$ 34,189
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock options exercised and restricted stock units issued including tax benefit			(1,678)
Restricted stock units expensed			8,171
Net income before noncontrolling interests	$ 118,444			118,307					137
Dividends				(13,749)
Change in unrealized investment gains, net of taxes	16,291				16,308
Unrealized gains (losses) on other-than-temporarily impaired securities					5
Change in unrealized currency translation adjustments	(47,805)					(47,805)
Stock exercised/vested								331
Stock repurchased								(91,213)
Contributions									111
Other comprehensive income (loss)	(31,514)					(47,805)	$ (31,514)		(22)
End of period at Mar. 31, 2015			998,005	5,836,968	322,512	(170,454)	152,058	(2,455,433)	34,415
Beginning and end of period at Dec. 31, 2015	4,633,208	$ 47,024	1,005,455	6,178,070	180,695	(247,393)		(2,563,605)	32,962
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock options exercised and restricted stock units issued including tax benefit			(652)
Restricted stock units expensed			8,769
Net income before noncontrolling interests	120,248			119,511					737
Dividends				(14,711)
Change in unrealized investment gains, net of taxes	76,855				76,904
Unrealized gains (losses) on other-than-temporarily impaired securities					(35)
Change in unrealized currency translation adjustments	(2,047)					(2,047)
Stock exercised/vested								652
Stock repurchased								(37,424)
Contributions									3,158
Other comprehensive income (loss)	74,808					(2,047)	74,808		(14)
End of period at Mar. 31, 2016	$ 4,788,056		$ 1,013,572	$ 6,282,870	$ 257,564	$ (249,440)	$ 8,124	$ (2,600,377)	$ 36,843