Condensed Consolidated Statements of Stockholders' Equity (USD $) In Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Net Unrealized Investment Gain (Loss) [Member]	Accumulated Other-than-Temporary Impairment Held-To-Maturity [Member]	Accumulated Other Than Temporary Impairment Available For Sale [Member]	Accumulated Translation Adjustment [Member]	Accumulated Defined Benefit Plans Adjustment [Member]	Retained Earnings [Member]
Total stockholders’ equity at Dec. 31, 2009		$ 3,626	$ 36,680		$ 31,639	$ (2,751)	$ (562)	$ 2,893	$ (13,459)	$ 1,055,987
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares exercised under stock option plan		0	0
Change in unrealized gains during period, net of tax	31,479				28,308
Cumulative effect of change in accounting principal						0
Amortization						80
Other-than-temporary Impairments, non-credit, net of tax						(26)
Additional Credit Loss On Previously Impaired Securities						50
Change in shadow deferred policy acquistion costs						(62)
Other-than-temporary Impairments, non-credit, net of tax							0
Recoveries, net of tax							326
Change in translation adjustments during period	(96)							(96)
Amortization of net prior service cost and net gain	579								579
Net earnings	39,220									39,220
Stockholder dividends										0
Total stockholders’ equity at Jun. 30, 2010	1,182,432	3,626	36,680	46,919	59,947	(2,709)	(236)	2,797	(12,880)	1,095,207
Total stockholders’ equity at Dec. 31, 2010	1,218,791	3,629	37,140		62,499	(2,713)	0	2,585	(11,963)	1,127,614
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares exercised under stock option plan		6	1,211
Change in unrealized gains during period, net of tax	5,775				3,703
Cumulative effect of change in accounting principal						0
Amortization						165
Other-than-temporary Impairments, non-credit, net of tax						0
Additional Credit Loss On Previously Impaired Securities						0
Change in shadow deferred policy acquistion costs						185
Other-than-temporary Impairments, non-credit, net of tax							0
Recoveries, net of tax							0
Change in translation adjustments during period	(134)							(134)
Amortization of net prior service cost and net gain	582								582
Net earnings	32,001									32,001
Stockholder dividends										0
Total stockholders’ equity at Jun. 30, 2011	$ 1,256,510	$ 3,635	$ 38,351	$ 54,909	$ 66,202	$ (2,363)	$ 0	$ 2,451	$ (11,381)	$ 1,159,615