Consolidation and Basis of Presentation (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Other net investment gains (losses)	$ 3,065	$ 1,779	$ 4,613	$ 4,153
Earnings before Federal income taxes	42,858	39,276	72,920	64,590
Federal income taxes	13,675	12,285	23,911	20,967
Net earnings	29,183	26,991	49,009	43,623
Unrealized Gains and Losses on Available-for-sale Securities [Member] | Amount Reclassified From Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Other net investment gains (losses)	2,993	1,720	3,682	3,834
Net OTTI losses recognized in earnings	0	(125)	(35)	(148)
Earnings before Federal income taxes	2,993	1,595	3,647	3,686
Federal income taxes	1,047	558	1,276	1,290
Net earnings	$ 1,946	$ 1,037	$ 2,371	$ 2,396