Consolidation and Basis of Presentation (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Other net investment gains (losses)	$ 611	$ 2,585
Earnings before Federal income taxes	33,573	35,463
Federal income taxes	6,698	11,925
Net earnings	26,875	23,538
Unrealized Gains and Losses on Available-for-sale Securities \| Amount Reclassified From Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Other net investment gains (losses)	40	1,061
Net OTTI losses recognized in earnings	0	0
Earnings before Federal income taxes	40	1,061
Federal income taxes	7	371
Net earnings	$ 33	$ 690

This item represents the net total realized and unrealized gain (loss) included in earnings for the period as a result of selling or holding marketable securities categorized as trading, available-for-sale, or held-to-maturity, including the unrealized holding gain (loss) of held-to-maturity securities transferred to the trading security category and the cumulative unrealized gain (loss) which was included in other comprehensive income (a separate component of shareholders' equity) for available-for-sale securities transferred to trading securities during the period. Additionally, this item would include any gains (losses) realized during the period from the sale of investments accounted for under the cost method of accounting.

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