Consolidation and Basis of Presentation (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Other net investment gains (losses)	$ 4,365	$ 3,065	$ 5,343	$ 4,613
Earnings before Federal income taxes	42,795	42,858	74,218	72,920
Federal income taxes	13,937	13,675	24,034	23,911
Net earnings	28,858	29,183	50,184	49,009
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)	2,961	2,993	3,215	3,682
Net OTTI losses recognized in earnings	(107)	0	(107)	(35)
Earnings before Federal income taxes	2,854	2,993	3,108	3,647
Federal income taxes	999	1,047	1,088	1,276
Net earnings	$ 1,855	$ 1,946	$ 2,020	$ 2,371