Consolidated Statements Of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 132,122	$ 130,672	$ 385,655	$ 378,337
Unrealized gains (losses) on securities:
Unrealized holding gains (losses) arising during period	(152,039)	352,906	(1,077,967)	631,743
Less: reclassification adjustment for (gains) losses on securities included in net income	(4,520)	(6,900)	(7,871)	(16,609)
Less: reclassification adjustment for amortization of (discount) and premium	(1,478)	1,348	(4,939)	1,224
Less: foreign exchange adjustment on securities marked to market	(4,097)	(6,966)	6,036	(6,569)
Unrealized gains (losses) on securities	(162,134)	340,388	(1,084,741)	609,789
Unrealized gains (losses) on other assets	1,754	1,814	(1,115)	2,828
Total unrealized gains (losses)	(160,380)	342,202	(1,085,856)	612,617
Less applicable taxes	56,150	(119,771)	381,262	(214,417)
Unrealized gains (losses), net of tax	(104,230)	222,431	(704,594)	398,200
Unrealized gains (losses) attributable to deferred acquisition costs	2,565	(1,219)	13,128	5,352
Less applicable taxes	(898)	427	(4,595)	(1,873)
Unrealized gains (losses) attributable to deferred acquisition costs, net of tax	1,667	(792)	8,533	3,479
Foreign exchange translation adjustments	4,138	3,707	(1,698)	3,619
Less applicable taxes	(1,324)	(1,154)	686	(1,265)
Foreign exchange translation adjustments, net of tax	2,814	2,553	(1,012)	2,354
Amortization of pension costs	4,605	3,569	13,756	10,678
Less applicable taxes	(1,613)	(1,250)	(4,815)	(3,737)
Amortization of pension costs, net of tax	2,992	2,319	8,941	6,941
Other comprehensive income (loss)	(96,757)	226,511	(688,132)	410,974
Comprehensive income (loss)	$ 35,365	$ 357,183	$ (302,477)	$ 789,311