Summary of Significant Accounting Policies (AOCI) (Details) - USD ($) $ in Thousands	3 Months Ended							12 Months Ended
	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Other net investment gains (losses)								$ 7,461	$ 11,755	$ 8,958
Earnings before Federal income taxes								146,668	157,521	141,697
Federal income taxes								48,272	51,933	45,450
Net earnings	$ 16,221	$ 28,858	$ 21,326	$ 28,113	$ 28,466	$ 29,183	$ 19,826	98,396	105,588	96,247
Accumulated other comprehensive income (loss) [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Other net investment gains (losses)								3,459	7,843	4,923
Net OTTI losses recognized in earnings								(252)	(150)	(213)
Earnings before Federal income taxes								3,207	7,693	4,710
Federal income taxes								1,122	2,693	1,649
Net earnings								$ 2,085	$ 5,000	$ 3,061