Segment and Other Operating Information (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2018 USD ($) customer	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Selected Condensed Consolidated Balance Sheet Items:
Total segment assets	$ 11,931,691				$ 12,225,094				$ 11,931,691	$ 12,225,094	$ 11,894,981
Other policyholder liabilities	135,694				128,009				135,694	128,009
Condensed Consolidated Income Statements:
Premiums and contract revenues									173,496	178,930	182,723
Net investment income									349,077	659,685	467,674
Other revenues									20,603	21,070	18,901
Realized gains (losses) on investments									8,423	14,763	13,070
Total revenues	42,486	$ 225,435	$ 174,658	$ 109,018	247,815	$ 203,990	$ 198,226	$ 224,417	551,599	874,448	682,368
Life and other policy benefits									65,297	71,485	65,529
Amortization of deferred policy acquisition costs									114,771	114,387	121,139
Universal life and annuity contract interest									136,055	437,019	248,390
Other operating expenses									93,969	107,002	94,448
Taxes on earnings from continuing operations									24,749	34,134	51,970
Net earnings	21,776	$ 35,641	$ 32,466	$ 26,875	39,587	$ 21,813	$ 25,483	$ 23,538	116,758	110,421	100,892
Revenues, excluding reinsurance premiums									194,256	199,242	202,398
Reinsurance premiums									(20,760)	(20,312)	(19,675)
United States
Condensed Consolidated Income Statements:
Revenues, excluding reinsurance premiums									82,614	74,937	75,405
Brazil
Condensed Consolidated Income Statements:
Revenues, excluding reinsurance premiums									27,280	33,024	38,928
Venezuela
Condensed Consolidated Income Statements:
Revenues, excluding reinsurance premiums									14,414	16,105	15,534
Taiwan
Condensed Consolidated Income Statements:
Revenues, excluding reinsurance premiums									12,864	14,844	14,474
Peru
Condensed Consolidated Income Statements:
Revenues, excluding reinsurance premiums									10,969	11,714	11,378
Chile
Condensed Consolidated Income Statements:
Revenues, excluding reinsurance premiums									8,769	9,201	8,859
Other foreign countries
Condensed Consolidated Income Statements:
Revenues, excluding reinsurance premiums									$ 37,346	39,417	37,820
Domestic Life Insurance
Condensed Consolidated Income Statements:
Number of customers | customer									3
Annuities
Condensed Consolidated Income Statements:
Number of customers | customer									2
Operating Segments
Selected Condensed Consolidated Balance Sheet Items:
Deferred policy acquisition costs and sales inducements	975,418				955,081				$ 975,418	955,081	982,305
Total segment assets	11,588,481				12,011,696				11,588,481	12,011,696	11,697,099
Future policy benefits	9,744,286				10,098,484				9,744,286	10,098,484	9,859,095
Other policyholder liabilities	135,694				128,009				135,694	128,009	143,391
Condensed Consolidated Income Statements:
Premiums and contract revenues									173,496	178,930	182,723
Net investment income									349,077	659,685	467,674
Other revenues									20,603	21,070	18,901
Total revenues									543,176	859,685	669,298
Life and other policy benefits									65,297	71,485	65,529
Amortization of deferred policy acquisition costs									114,771	114,387	121,139
Universal life and annuity contract interest									136,055	437,019	248,390
Other operating expenses									93,969	107,002	94,448
Federal income taxes (benefit)									22,980	28,967	47,395
Total expenses									433,072	758,860	576,901
Segment earnings (loss)									110,104	100,825	92,397
Net earnings									110,104	100,825
Operating Segments | Domestic Life Insurance
Selected Condensed Consolidated Balance Sheet Items:
Deferred policy acquisition costs and sales inducements	122,661				101,253				122,661	101,253	90,485
Total segment assets	1,215,864				1,106,410				1,215,864	1,106,410	971,990
Future policy benefits	1,039,150				950,884				1,039,150	950,884	830,460
Other policyholder liabilities	17,439				13,643				17,439	13,643	13,998
Condensed Consolidated Income Statements:
Premiums and contract revenues									40,879	37,387	34,728
Net investment income									23,579	73,866	39,691
Other revenues									19	46	119
Total revenues									64,477	111,299	74,538
Life and other policy benefits									21,688	18,565	17,908
Amortization of deferred policy acquisition costs									11,539	10,377	4,125
Universal life and annuity contract interest									8,826	59,865	28,606
Other operating expenses									20,731	18,842	18,739
Federal income taxes (benefit)									292	815	1,749
Total expenses									63,076	108,464	71,127
Segment earnings (loss)									1,401	2,835	3,411
Operating Segments | International Life Insurance
Selected Condensed Consolidated Balance Sheet Items:
Deferred policy acquisition costs and sales inducements	243,518				250,128				243,518	250,128	243,106
Total segment assets	1,211,036				1,236,733				1,211,036	1,236,733	1,232,648
Future policy benefits	894,891				915,384				894,891	915,384	919,380
Other policyholder liabilities	20,381				11,318				20,381	11,318	10,528
Condensed Consolidated Income Statements:
Premiums and contract revenues									108,923	120,852	125,775
Net investment income									22,603	68,399	42,331
Other revenues									87	83	321
Total revenues									131,613	189,334	168,427
Life and other policy benefits									22,333	23,981	18,759
Amortization of deferred policy acquisition costs									24,358	(1,473)	18,027
Universal life and annuity contract interest									24,590	54,502	28,636
Other operating expenses									19,593	36,341	25,933
Federal income taxes (benefit)									7,035	16,958	26,130
Total expenses									97,909	130,309	117,485
Segment earnings (loss)									33,704	59,025	50,942
Operating Segments | Annuities
Selected Condensed Consolidated Balance Sheet Items:
Deferred policy acquisition costs and sales inducements	609,239				603,700				609,239	603,700	648,714
Total segment assets	8,791,463				9,269,956				8,791,463	9,269,956	9,193,980
Future policy benefits	7,810,245				8,232,216				7,810,245	8,232,216	8,109,255
Other policyholder liabilities	97,874				103,048				97,874	103,048	118,865
Condensed Consolidated Income Statements:
Premiums and contract revenues									23,694	20,691	22,220
Net investment income									276,123	490,706	362,700
Other revenues									66	109	254
Total revenues									299,883	511,506	385,174
Life and other policy benefits									21,276	28,939	28,862
Amortization of deferred policy acquisition costs									78,874	105,483	98,987
Universal life and annuity contract interest									102,639	322,652	191,148
Other operating expenses									32,584	32,021	31,852
Federal income taxes (benefit)									11,139	5,002	11,638
Total expenses									246,512	494,097	362,487
Segment earnings (loss)									53,371	17,409	22,687
Operating Segments | All Others
Selected Condensed Consolidated Balance Sheet Items:
Deferred policy acquisition costs and sales inducements	0				0				0	0	0
Total segment assets	370,118				398,597				370,118	398,597	298,481
Future policy benefits	0				0				0	0	0
Other policyholder liabilities	0				0				0	0	0
Condensed Consolidated Income Statements:
Premiums and contract revenues									0	0	0
Net investment income									26,772	26,714	22,952
Other revenues									20,431	20,832	18,207
Total revenues									47,203	47,546	41,159
Life and other policy benefits									0	0	0
Amortization of deferred policy acquisition costs									0	0	0
Universal life and annuity contract interest									0	0	0
Other operating expenses									21,061	19,798	17,924
Federal income taxes (benefit)									4,514	6,192	7,878
Total expenses									25,575	25,990	25,802
Segment earnings (loss)									21,628	21,556	15,357
Segment Reconciling Items
Selected Condensed Consolidated Balance Sheet Items:
Total segment assets	$ 343,210				$ 213,398				343,210	213,398	197,882
Condensed Consolidated Income Statements:
Taxes on realized gains (losses) on investments									1,769	5,167	4,575
Realized gains (losses) on investments, net of taxes									$ 6,654	$ 9,596	$ 8,495
Agency Two | Domestic Life Insurance
Condensed Consolidated Income Statements:
Major customer, percentage of sales									10.00%
Agency Two | Annuities
Condensed Consolidated Income Statements:
Major customer, percentage of sales									13.00%
Agency One | Domestic Life Insurance
Condensed Consolidated Income Statements:
Major customer, percentage of sales									35.00%
Agency One | Annuities
Condensed Consolidated Income Statements:
Major customer, percentage of sales									14.00%
Agency Three | Domestic Life Insurance
Condensed Consolidated Income Statements:
Major customer, percentage of sales									10.00%