Segment and Other Operating Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Selected Condensed Consolidated Balance Sheet Items:
Total segment assets	$ 11,096,081	$ 10,512,777	$ 11,096,081	$ 10,512,777	$ 10,830,416
Other policyholder liabilities	149,714		149,714		142,587
Condensed Consolidated Income Statements:
Premiums and contract revenues	43,386	45,581	85,662	87,344
Net investment income	155,179	129,687	263,630	310,501
Other revenues	5,211	5,990	10,974	12,132
Realized gains (losses) on investments	3,065	1,601	4,578	3,914
Total condensed consolidated premiums and other revenues	206,841	182,859	364,844	413,891
Life and other policy benefits	14,796	18,450	27,759	31,140
Amortization of deferred acquisition costs	27,258	28,852	55,837	59,656
Universal life and annuity contract interest	102,429	71,438	165,365	211,738
Other operating expenses	19,500	24,843	42,963	46,767
Federal income taxes (benefit)	12,602	11,725	22,309	19,597
Taxes on realized gains (losses) on investments	1,073	560	1,602	1,370
Total condensed consolidated Federal income taxes	13,675	12,285	23,911	20,967
Segment earnings (loss)	27,191	25,950	46,033	41,079
Realized gains (losses) on investments, net of taxes	1,992	1,041	2,976	2,544
Net earnings	29,183	26,991	49,009	43,623
Segments [Member]
Selected Condensed Consolidated Balance Sheet Items:
Deferred policy acquisition costs and sales inducements	933,673	920,089	933,673	920,089
Total segment assets	10,924,254	10,330,795	10,924,254	10,330,795
Future policy benefits	9,292,785	8,807,639	9,292,785	8,807,639
Other policyholder liabilities	149,714	165,230	149,714	165,230
Condensed Consolidated Income Statements:
Premiums and contract revenues	43,386	45,581	85,662	87,344
Net investment income	155,179	129,687	263,630	310,501
Other revenues	5,211	5,990	10,974	12,132
Total condensed consolidated premiums and other revenues	203,776	181,258	360,266	409,977
Life and other policy benefits	14,796	18,450	27,759	31,140
Amortization of deferred acquisition costs	27,258	28,852	55,837	59,656
Universal life and annuity contract interest	102,429	71,438	165,365	211,738
Other operating expenses	19,500	24,843	42,963	46,767
Federal income taxes (benefit)	12,602	11,725	22,309	19,597
Total expenses	176,585	155,308	314,233	368,898
Segment earnings (loss)	27,191	25,950	46,033	41,079
Segments [Member] | Domestic Life Insurance [Member]
Selected Condensed Consolidated Balance Sheet Items:
Deferred policy acquisition costs and sales inducements	57,354	45,391	57,354	45,391
Total segment assets	670,565	522,003	670,565	522,003
Future policy benefits	581,946	454,359	581,946	454,359
Other policyholder liabilities	13,259	13,109	13,259	13,109
Condensed Consolidated Income Statements:
Premiums and contract revenues	7,065	9,413	15,230	19,023
Net investment income	10,902	8,242	17,185	16,015
Other revenues	3	(3)	21	9
Total condensed consolidated premiums and other revenues	17,970	17,652	32,436	35,047
Life and other policy benefits	1,423	1,096	3,915	4,126
Amortization of deferred acquisition costs	1,780	2,210	4,180	4,245
Universal life and annuity contract interest	8,158	7,868	13,263	15,059
Other operating expenses	3,992	4,947	8,271	8,714
Federal income taxes (benefit)	851	468	916	938
Total expenses	16,204	16,589	30,545	33,082
Segment earnings (loss)	1,766	1,063	1,891	1,965
Segments [Member] | International Life Insurance [Member]
Selected Condensed Consolidated Balance Sheet Items:
Deferred policy acquisition costs and sales inducements	238,211	231,684	238,211	231,684
Total segment assets	1,229,589	1,134,181	1,229,589	1,134,181
Future policy benefits	934,791	875,672	934,791	875,672
Other policyholder liabilities	12,399	14,734	12,399	14,734
Condensed Consolidated Income Statements:
Premiums and contract revenues	29,663	30,177	58,771	58,196
Net investment income	16,911	13,637	27,629	32,267
Other revenues	60	108	301	151
Total condensed consolidated premiums and other revenues	46,634	43,922	86,701	90,614
Life and other policy benefits	1,668	3,225	6,703	6,870
Amortization of deferred acquisition costs	8,808	7,926	15,553	13,713
Universal life and annuity contract interest	15,659	9,244	25,864	31,235
Other operating expenses	4,835	6,125	11,860	12,833
Federal income taxes (benefit)	4,963	5,456	8,722	8,386
Total expenses	35,933	31,976	68,702	73,037
Segment earnings (loss)	10,701	11,946	17,999	17,577
Segments [Member] | Annuities [Member]
Selected Condensed Consolidated Balance Sheet Items:
Deferred policy acquisition costs and sales inducements	638,108	643,014	638,108	643,014
Total segment assets	8,749,666	8,420,780	8,749,666	8,420,780
Future policy benefits	7,776,048	7,477,608	7,776,048	7,477,608
Other policyholder liabilities	124,056	137,387	124,056	137,387
Condensed Consolidated Income Statements:
Premiums and contract revenues	6,658	5,991	11,661	10,125
Net investment income	122,666	102,805	209,283	253,183
Other revenues	3	(9)	40	30
Total condensed consolidated premiums and other revenues	129,327	108,787	220,984	263,338
Life and other policy benefits	11,705	14,129	17,141	20,144
Amortization of deferred acquisition costs	16,670	18,716	36,104	41,698
Universal life and annuity contract interest	78,612	54,326	126,238	165,444
Other operating expenses	5,824	8,466	12,920	14,552
Federal income taxes (benefit)	5,227	4,087	9,329	6,944
Total expenses	118,038	99,724	201,732	248,782
Segment earnings (loss)	11,289	9,063	19,252	14,556
Segments [Member] | All Others [Member]
Selected Condensed Consolidated Balance Sheet Items:
Deferred policy acquisition costs and sales inducements	0	0	0	0
Total segment assets	274,434	253,831	274,434	253,831
Future policy benefits	0	0	0	0
Other policyholder liabilities	0	0	0	0
Condensed Consolidated Income Statements:
Premiums and contract revenues	0	0	0	0
Net investment income	4,700	5,003	9,533	9,036
Other revenues	5,145	5,894	10,612	11,942
Total condensed consolidated premiums and other revenues	9,845	10,897	20,145	20,978
Life and other policy benefits	0	0	0	0
Amortization of deferred acquisition costs	0	0	0	0
Universal life and annuity contract interest	0	0	0	0
Other operating expenses	4,849	5,305	9,912	10,668
Federal income taxes (benefit)	1,561	1,714	3,342	3,329
Total expenses	6,410	7,019	13,254	13,997
Segment earnings (loss)	3,435	3,878	6,891	6,981
Other unallocated [Member]
Selected Condensed Consolidated Balance Sheet Items:
Total segment assets	$ 171,827	$ 181,982	$ 171,827	$ 181,982