Consolidated Statement of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Statement of Income and Comprehensive Income [Abstract]
Net earnings	$ 105,850	$ 82,584
Investment gains (losses):
Investment gains (losses) during the period	(30,395)	21,640
Income tax charge (benefit)	(10,327)	7,303
Investments gains (losses), net of tax	(20,068)	14,337
Less reclassification adjustments for:
Gains included in net earnings	8,570	171
Income tax charge	2,999	60
Total reclassifications	5,571	111
Net unrealized investment gains (losses)	(25,639)	14,226
Foreign currency translation adjustment	(2,056)	2,533
Income tax charge (benefit)	(524)	123
Foreign currency translation adjustment, net of tax	(1,532)	2,410
Other comprehensive income (loss)	(27,171)	16,636
Comprehensive income	$ 78,679	$ 99,220