Consolidation and Basis of Presentation (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Other net investment gains (losses)	$ 2,169	$ 3,298	$ 6,782	$ 7,451
Earnings before Federal income taxes	43,328	36,846	116,248	101,436
Federal income taxes	14,862	12,064	38,773	33,031
Net earnings	28,466	24,782	77,475	68,405
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)	1,474	413	5,156	4,247
Net OTTI losses recognized in earnings	0	(12)	(35)	(160)
Earnings before Federal income taxes	1,474	401	5,121	4,087
Federal income taxes	516	140	1,792	1,430
Net earnings	$ 958	$ 261	$ 3,329	$ 2,657