Consolidated Statement of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Statement of Income and Comprehensive Income [Abstract]
Net earnings	$ 107,062	$ 60,437	$ 283,139	$ 176,905
Investment gains (losses)
Investment gains (losses) during the year	91,185	100,555	152,498	155,933
Income tax charge (benefit)	32,274	36,059	54,078	51,356
Investments gains (losses), net of tax	58,911	64,496	98,420	104,577
Less reclassification adjustments for
Other Comprehensive Income (Loss), Reclassification Adjustment for Sale of Securities Included in Net Income, before Tax	832	2,672	7,491	(306)
OtherComprehensiveIncomeReclassificationAdjustmentForSaleOfSecuritiesIncludedInNetIncomeTax	291	935	2,622	(107)
Other Comprehensive Income (Loss), Reclassification Adjustment for Sale of Securities Included in Net Income, Net of Tax	541	1,737	4,869	(199)
Net unrealized investment gains (losses)	58,370	62,759	93,551	104,776
Foreign currency translation adjustment	(141)	(6,297)	(3,454)	1,865
Income tax charge (benefit)	(234)	331	(483)	1,809
Foreign currency translation adjustment, net of tax	93	(6,628)	(2,971)	56
Other comprehensive income (loss)	58,463	56,131	90,580	104,832
Comprehensive income	$ 165,525	$ 116,568	$ 373,719	$ 281,737