Segment and Other Operating Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Selected Condensed Consolidated Balance Sheet Items:
Deferred policy acquisition costs and sales inducements	$ 858,241				$ 878,295				$ 858,241	$ 878,295	$ 835,783
Total segment assets	10,081,280				9,650,933				10,081,280	9,650,933	8,723,875
Future policy benefits	8,568,854				8,163,455				8,568,854	8,163,455	7,247,781
Other policyholder liabilities	148,561				151,308				148,561	151,308	151,526
Other unallocated assets	182,578				77,066				182,578	77,066	50,073
Total assets	10,263,858				9,727,999				10,263,858	9,727,999	8,773,948
Condensed Consolidated Income Statements:
Premiums and contract revenues									167,944	150,211	143,757
Net investment income									460,048	391,034	401,383
Other revenues									23,470	25,439	25,377
Realized gains (losses) on investments									13,200	6,063	5,475
Total revenues									651,462	566,684	570,517
Revenues	149,407	190,985	127,609	196,662	159,875	92,354	140,151	180,367	664,662	572,747	575,992
Life and other policy benefits									51,842	46,494	52,929
Amortization of deferred policy acquisition costs									121,922	133,088	96,449	96,449
Universal life and annuity contract interest									262,339	232,788	266,603
Other operating expenses									87,978	77,541	55,448
Federal income taxes (benefit)									43,403	25,087	29,750
Taxes on realized gains (losses) on investments									4,620	2,122	1,916
Income Tax Expense (Benefit)									48,023	27,209	31,666
Total expenses									567,484	514,998	501,179
Segment earnings (loss)									83,978	51,686	69,338
Realized gains (losses) on investments, net of taxes									8,580	3,941	3,559
Net earnings	25,249	24,322	23,246	19,741	4,362	19,265	13,790	18,211	92,558	55,627	72,897
Revenues, excluding reinsurance premiums									187,728	170,864	165,635
Reinsurance premiums									(19,784)	(20,653)	(21,878)
United States [Member]
Condensed Consolidated Income Statements:
Revenues, excluding reinsurance premiums									67,924	58,570	57,190
Brazil [Member]
Condensed Consolidated Income Statements:
Revenues, excluding reinsurance premiums									38,605	34,367	31,015
Taiwan [Member]
Condensed Consolidated Income Statements:
Revenues, excluding reinsurance premiums									13,958	13,155	12,421
Argentina [Member]
Condensed Consolidated Income Statements:
Revenues, excluding reinsurance premiums									12,223	10,348	9,639
Venezuela [Member]
Condensed Consolidated Income Statements:
Revenues, excluding reinsurance premiums									9,818	9,413	10,205
Chile [Member]
Condensed Consolidated Income Statements:
Revenues, excluding reinsurance premiums									8,693	8,820	8,600
Other foreign countries [Member]
Condensed Consolidated Income Statements:
Revenues, excluding reinsurance premiums									36,507	36,191	36,565
Domestic Life Insurance [Member]
Selected Condensed Consolidated Balance Sheet Items:
Deferred policy acquisition costs and sales inducements	40,810				37,102				40,810	37,102	42,751
Total segment assets	463,569				403,868				463,569	403,868	387,873
Future policy benefits	398,202				344,916				398,202	344,916	325,246
Other policyholder liabilities	10,468				9,526				10,468	9,526	13,394
Condensed Consolidated Income Statements:
Premiums and contract revenues									31,143	30,387	27,622
Net investment income									21,194	16,980	17,226
Other revenues									62	69	167
Total revenues									52,399	47,436	45,015
Life and other policy benefits									10,633	11,636	13,484
Amortization of deferred policy acquisition costs									7,461	11,467	9,352
Universal life and annuity contract interest									17,507	9,760	10,643
Other operating expenses									14,895	13,890	12,839
Federal income taxes (benefit)									648	223	(391)
Total expenses									51,144	46,976	45,927
Segment earnings (loss)									1,255	460	(912)
International Life Insurance [Member]
Selected Condensed Consolidated Balance Sheet Items:
Deferred policy acquisition costs and sales inducements	226,899				231,123				226,899	231,123	226,004
Total segment assets	1,105,862				1,023,942				1,105,862	1,023,942	1,025,103
Future policy benefits	846,028				761,926				846,028	761,926	716,716
Other policyholder liabilities	13,074				17,400				13,074	17,400	26,678
Condensed Consolidated Income Statements:
Premiums and contract revenues									114,605	98,021	98,092
Net investment income									43,469	36,806	38,667
Other revenues									485	354	358
Total revenues									158,559	135,181	137,117
Life and other policy benefits									20,877	20,709	29,228
Amortization of deferred policy acquisition costs									18,103	29,415	21,828
Universal life and annuity contract interest									39,639	36,674	36,369
Other operating expenses									26,007	22,131	18,651
Federal income taxes (benefit)									18,377	8,578	9,319
Total expenses									123,003	117,507	115,395
Segment earnings (loss)									35,556	17,674	21,722
Annuities [Member]
Selected Condensed Consolidated Balance Sheet Items:
Deferred policy acquisition costs and sales inducements	590,532				610,070				590,532	610,070	567,028
Total segment assets	8,269,445				7,997,407				8,269,445	7,997,407	7,101,720
Future policy benefits	7,324,624				7,056,613				7,324,624	7,056,613	6,205,819
Other policyholder liabilities	125,019				124,382				125,019	124,382	111,454
Condensed Consolidated Income Statements:
Premiums and contract revenues									22,196	21,803	18,043
Net investment income									375,431	318,294	327,975
Other revenues									80	3,170	2,002
Total revenues									397,707	343,267	348,020
Life and other policy benefits									20,332	14,149	10,217
Amortization of deferred policy acquisition costs									96,358	92,206	65,269
Universal life and annuity contract interest									205,193	186,354	219,591
Other operating expenses									25,456	20,474	3,905
Federal income taxes (benefit)									17,162	9,831	14,722
Total expenses									364,501	323,014	313,704
Segment earnings (loss)									33,206	20,253	34,316
Major customer, percentage of sales									16.00%
All Others [Member]
Selected Condensed Consolidated Balance Sheet Items:
Deferred policy acquisition costs and sales inducements	0				0				0	0	0
Total segment assets	242,404				225,716				242,404	225,716	209,179
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									19,954	18,954	17,515
Other revenues									22,843	21,846	22,850
Total revenues									42,797	40,800	40,365
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									21,620	21,046	20,053
Federal income taxes (benefit)									7,216	6,455	6,100
Total expenses									28,836	27,501	26,153
Segment earnings (loss)									$ 13,961	$ 13,299	$ 14,212