Segment and Other Operating Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Selected Condensed Consolidated Balance Sheet Items:
Total segment assets	$ 10,668,468	$ 10,166,094	$ 10,668,468	$ 10,166,094	$ 10,263,858
Other policyholder liabilities	159,822		159,822		148,561
Condensed Consolidated Income Statements:
Premiums and contract revenues	37,682	41,048	125,026	122,887
Net investment income	141,403	139,074	451,904	366,813
Other revenues	5,822	5,923	17,954	17,444
Realized gains (losses) on investments	3,285	4,940	7,199	8,112
Total condensed consolidated premiums and other revenues	188,192	190,985	602,083	515,256
Life and other policy benefits	16,941	12,323	48,081	39,858
Amortization of deferred acquisition costs	24,244	28,403	83,900	91,463
Universal life and annuity contract interest	87,486	89,386	299,224	216,933
Other operating expenses	22,675	22,143	69,442	64,613
Federal income taxes (benefit)	10,913	12,679	30,511	32,241
Taxes on realized gains (losses) on investments	1,151	1,729	2,520	2,839
Total condensed consolidated Federal income taxes	12,064	14,408	33,031	35,080
Segment earnings (loss)	22,648	21,111	63,726	62,036
Realized gains (losses) on investments, net of taxes	2,134	3,211	4,679	5,273
Net earnings	24,782	24,322	68,405	67,309
Segments [Member]
Selected Condensed Consolidated Balance Sheet Items:
Deferred policy acquisition costs and sales inducements	936,515	849,222	936,515	849,222
Total segment assets	10,462,353	10,103,615	10,462,353	10,103,615
Future policy benefits	8,934,285	8,467,600	8,934,285	8,467,600
Other policyholder liabilities	159,822	152,725	159,822	152,725
Condensed Consolidated Income Statements:
Premiums and contract revenues	37,682	41,048	125,026	122,887
Net investment income	141,403	139,074	451,904	366,813
Other revenues	5,822	5,923	17,954	17,444
Total condensed consolidated premiums and other revenues	184,907	186,045	594,884	507,144
Life and other policy benefits	16,941	12,323	48,081	39,858
Amortization of deferred acquisition costs	24,244	28,403	83,900	91,463
Universal life and annuity contract interest	87,486	89,386	299,224	216,933
Other operating expenses	22,675	22,143	69,442	64,613
Federal income taxes (benefit)	10,913	12,679	30,511	32,241
Total expenses	162,259	164,934	531,158	445,108
Segment earnings (loss)	22,648	21,111	63,726	62,036
Segments [Member] | Domestic Life Insurance [Member]
Selected Condensed Consolidated Balance Sheet Items:
Deferred policy acquisition costs and sales inducements	50,067	38,052	50,067	38,052
Total segment assets	559,824	450,649	559,824	450,649
Future policy benefits	485,754	380,752	485,754	380,752
Other policyholder liabilities	13,177	13,401	13,177	13,401
Condensed Consolidated Income Statements:
Premiums and contract revenues	3,944	7,680	22,967	22,499
Net investment income	6,928	6,037	22,943	15,846
Other revenues	12	(46)	21	6
Total condensed consolidated premiums and other revenues	10,884	13,671	45,931	38,351
Life and other policy benefits	4,003	4,482	8,129	7,750
Amortization of deferred acquisition costs	1,015	437	5,260	4,896
Universal life and annuity contract interest	2,261	2,976	17,320	11,419
Other operating expenses	2,782	3,313	11,496	10,659
Federal income taxes (benefit)	268	865	1,206	1,241
Total expenses	10,329	12,073	43,411	35,965
Segment earnings (loss)	555	1,598	2,520	2,386
Segments [Member] | International Life Insurance [Member]
Selected Condensed Consolidated Balance Sheet Items:
Deferred policy acquisition costs and sales inducements	235,922	224,814	235,922	224,814
Total segment assets	1,161,517	1,111,039	1,161,517	1,111,039
Future policy benefits	899,090	821,178	899,090	821,178
Other policyholder liabilities	16,778	11,536	16,778	11,536
Condensed Consolidated Income Statements:
Premiums and contract revenues	28,865	28,453	87,061	83,999
Net investment income	10,957	12,255	43,224	34,967
Other revenues	60	32	211	378
Total condensed consolidated premiums and other revenues	39,882	40,740	130,496	119,344
Life and other policy benefits	11,040	4,827	17,910	14,622
Amortization of deferred acquisition costs	3,287	2,083	17,000	15,448
Universal life and annuity contract interest	8,525	9,602	39,760	30,845
Other operating expenses	5,987	7,069	18,820	19,605
Federal income taxes (benefit)	3,596	6,271	11,982	13,277
Total expenses	32,435	29,852	105,472	93,797
Segment earnings (loss)	7,447	10,888	25,024	25,547
Segments [Member] | Annuities [Member]
Selected Condensed Consolidated Balance Sheet Items:
Deferred policy acquisition costs and sales inducements	650,526	586,356	650,526	586,356
Total segment assets	8,487,915	8,302,668	8,487,915	8,302,668
Future policy benefits	7,549,441	7,265,670	7,549,441	7,265,670
Other policyholder liabilities	129,867	127,788	129,867	127,788
Condensed Consolidated Income Statements:
Premiums and contract revenues	4,873	4,915	14,998	16,389
Net investment income	118,521	115,781	371,704	302,045
Other revenues	22	213	52	14
Total condensed consolidated premiums and other revenues	123,416	120,909	386,754	318,448
Life and other policy benefits	1,898	3,014	22,042	17,486
Amortization of deferred acquisition costs	19,942	25,883	61,640	71,119
Universal life and annuity contract interest	76,700	76,808	242,144	174,669
Other operating expenses	8,565	7,332	23,117	19,104
Federal income taxes (benefit)	5,298	3,215	12,242	12,335
Total expenses	112,403	116,252	361,185	294,713
Segment earnings (loss)	11,013	4,657	25,569	23,735
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	253,097	239,259	253,097	239,259
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	4,997	5,001	14,033	13,955
Other revenues	5,728	5,724	17,670	17,046
Total condensed consolidated premiums and other revenues	10,725	10,725	31,703	31,001
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	5,341	4,429	16,009	15,245
Federal income taxes (benefit)	1,751	2,328	5,081	5,388
Total expenses	7,092	6,757	21,090	20,633
Segment earnings (loss)	3,633	3,968	10,613	10,368
Other unallocated [Member]
Selected Condensed Consolidated Balance Sheet Items:
Total segment assets	$ 206,115	$ 62,479	$ 206,115	$ 62,479