Segment and Other Operating Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Selected Condensed Consolidated Balance Sheet Items:
Total segment assets	$ 11,515,294,000	$ 11,096,081,000	$ 11,515,294,000	$ 11,096,081,000	$ 11,351,892,000
Other policyholder liabilities	143,781,000		143,781,000		$ 139,222,000
Condensed Consolidated Income Statements:
Premiums and contract revenues	43,507,000	43,386,000	85,167,000	85,662,000
Net investment income	102,259,000	155,179,000	202,182,000	263,630,000
Other revenues	5,194,000	5,211,000	10,523,000	10,974,000
Realized gains (losses) on investments	4,258,000	3,065,000	5,236,000	4,578,000
Total condensed consolidated premiums and other revenues	155,218,000	206,841,000	303,108,000	364,844,000
Life and other policy benefits	16,120,000	14,796,000	35,386,000	27,759,000
Amortization of deferred acquisition costs	28,070,000	27,258,000	55,722,000	55,837,000
Universal life and annuity contract interest	49,431,000	102,429,000	98,470,000	165,365,000
Other operating expenses	18,802,000	19,500,000	39,312,000	42,963,000
Federal income taxes (benefit)	12,446,000	12,602,000	22,201,000	22,309,000
Taxes on realized gains (losses) on investments	1,491,000	1,073,000	1,833,000	1,602,000
Total condensed consolidated Federal income taxes	13,937,000	13,675,000	24,034,000	23,911,000
Segment earnings (loss)	26,091,000	27,191,000	46,781,000	46,033,000
Realized gains (losses) on investments, net of taxes	2,767,000	1,992,000	3,403,000	2,976,000
Net earnings	28,858,000	29,183,000	50,184,000	49,009,000
Segments [Member]
Selected Condensed Consolidated Balance Sheet Items:
Deferred policy acquisition costs and sales inducements	982,454,000	933,673,000	982,454,000	933,673,000
Total segment assets	11,324,301,000	10,924,254,000	11,324,301,000	10,924,254,000
Future policy benefits	9,621,531,000	9,292,785,000	9,621,531,000	9,292,785,000
Other policyholder liabilities	143,781,000	149,714,000	143,781,000	149,714,000
Condensed Consolidated Income Statements:
Premiums and contract revenues	43,507,000	43,386,000	85,167,000	85,662,000
Net investment income	102,259,000	155,179,000	202,182,000	263,630,000
Other revenues	5,194,000	5,211,000	10,523,000	10,974,000
Total condensed consolidated premiums and other revenues	150,960,000	203,776,000	297,872,000	360,266,000
Life and other policy benefits	16,120,000	14,796,000	35,386,000	27,759,000
Amortization of deferred acquisition costs	28,070,000	27,258,000	55,722,000	55,837,000
Universal life and annuity contract interest	49,431,000	102,429,000	98,470,000	165,365,000
Other operating expenses	18,802,000	19,500,000	39,312,000	42,963,000
Federal income taxes (benefit)	12,446,000	12,602,000	22,201,000	22,309,000
Total expenses	124,869,000	176,585,000	251,091,000	314,233,000
Segment earnings (loss)	26,091,000	27,191,000	46,781,000	46,033,000
Segments [Member] | Domestic Life Insurance [Member]
Selected Condensed Consolidated Balance Sheet Items:
Deferred policy acquisition costs and sales inducements	70,561,000	57,354,000	70,561,000	57,354,000
Total segment assets	811,768,000	670,565,000	811,768,000	670,565,000
Future policy benefits	702,620,800	581,946,000	702,620,800	581,946,000
Other policyholder liabilities	11,846,000	13,259,000	11,846,000	13,259,000
Condensed Consolidated Income Statements:
Premiums and contract revenues	7,937,000	7,065,000	14,424,000	15,230,000
Net investment income	8,005,000	10,902,000	15,170,000	17,185,000
Other revenues	4,000	3,000	20,000	21,000
Total condensed consolidated premiums and other revenues	15,946,000	17,970,000	29,614,000	32,436,000
Life and other policy benefits	3,882,000	1,423,000	8,995,000	3,915,000
Amortization of deferred acquisition costs	1,698,000	1,780,000	4,879,000	4,180,000
Universal life and annuity contract interest	5,460,000	8,158,000	10,399,000	13,263,000
Other operating expenses	3,442,000	3,992,000	7,157,000	8,271,000
Federal income taxes (benefit)	467,000	851,000	(584,000)	916,000
Total expenses	14,949,000	16,204,000	30,846,000	30,545,000
Segment earnings (loss)	997,000	1,766,000	(1,232,000)	1,891,000
Segments [Member] | International Life Insurance [Member]
Selected Condensed Consolidated Balance Sheet Items:
Deferred policy acquisition costs and sales inducements	254,785,000	238,211,000	254,785,000	238,211,000
Total segment assets	1,247,941,000	1,229,589,000	1,247,941,000	1,229,589,000
Future policy benefits	954,684,000	934,791,000	954,684,000	934,791,000
Other policyholder liabilities	16,398,000	12,399,000	16,398,000	12,399,000
Condensed Consolidated Income Statements:
Premiums and contract revenues	29,364,000	29,663,000	59,697,000	58,771,000
Net investment income	8,785,000	16,911,000	17,399,000	27,629,000
Other revenues	(25,000)	60,000	61,000	301,000
Total condensed consolidated premiums and other revenues	38,124,000	46,634,000	77,157,000	86,701,000
Life and other policy benefits	5,587,000	1,668,000	11,792,000	6,703,000
Amortization of deferred acquisition costs	5,163,000	8,808,000	4,513,000	15,553,000
Universal life and annuity contract interest	6,927,000	15,659,000	14,057,000	25,864,000
Other operating expenses	5,212,000	4,835,000	11,134,000	11,860,000
Federal income taxes (benefit)	4,932,000	4,963,000	11,477,000	8,722,000
Total expenses	27,821,000	35,933,000	52,973,000	68,702,000
Segment earnings (loss)	10,303,000	10,701,000	24,184,000	17,999,000
Segments [Member] | Annuities [Member]
Selected Condensed Consolidated Balance Sheet Items:
Deferred policy acquisition costs and sales inducements	657,108,000	638,108,000	657,108,000	638,108,000
Total segment assets	9,000,323,000	8,749,666,000	9,000,323,000	8,749,666,000
Future policy benefits	7,964,226,000	7,776,048,000	7,964,226,000	7,776,048,000
Other policyholder liabilities	115,537,000	124,056,000	115,537,000	124,056,000
Condensed Consolidated Income Statements:
Premiums and contract revenues	6,206,000	6,658,000	11,046,000	11,661,000
Net investment income	79,509,000	122,666,000	158,745,000	209,283,000
Other revenues	4,000	3,000	19,000	40,000
Total condensed consolidated premiums and other revenues	85,719,000	129,327,000	169,810,000	220,984,000
Life and other policy benefits	6,651,000	11,705,000	14,599,000	17,141,000
Amortization of deferred acquisition costs	21,209,000	16,670,000	46,330,000	36,104,000
Universal life and annuity contract interest	37,044,000	78,612,000	74,014,000	126,238,000
Other operating expenses	5,434,000	5,824,000	11,612,000	12,920,000
Federal income taxes (benefit)	4,961,000	5,227,000	7,484,000	9,329,000
Total expenses	75,299,000	118,038,000	154,039,000	201,732,000
Segment earnings (loss)	10,420,000	11,289,000	15,771,000	19,252,000
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	264,269,000	274,434,000	264,269,000	274,434,000
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	5,960,000	4,700,000	10,868,000	9,533,000
Other revenues	5,211,000	5,145,000	10,423,000	10,612,000
Total condensed consolidated premiums and other revenues	11,171,000	9,845,000	21,291,000	20,145,000
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	4,714,000	4,849,000	9,409,000	9,912,000
Federal income taxes (benefit)	2,086,000	1,561,000	3,824,000	3,342,000
Total expenses	6,800,000	6,410,000	13,233,000	13,254,000
Segment earnings (loss)	4,371,000	3,435,000	8,058,000	6,891,000
Other unallocated [Member]
Selected Condensed Consolidated Balance Sheet Items:
Total segment assets	$ 190,993,000	$ 171,827,000	$ 190,993,000	$ 171,827,000