Business Segments - Analysis of Profitability by Segment (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Segment Reporting Information [Line Items]
Pretax operating income									$ 788,804	$ 753,592	$ 732,035
Applicable taxes									(258,137)	(246,945)	(238,335)
Net operating income									530,667	506,647	493,700
Realized gains (losses)-investments (after tax)									3,965	24,591	16,838
Loss on disposal of discontinued operations (after tax)									0	0	(455)
Acquisition expense and adjustments-Family Heritage (after tax)									522	(1,914)	0
Legal settlement expenses (after tax)									(5,931)	0	(7,800)
Guaranty Fund assessment (after tax)									(751)	0	0
State administrative settlement (after tax)									0	0	(4,486)
Loss on sale of equipment (after tax)									0	0	(636)
Net income	142,817	132,122	133,901	119,632	150,987	130,672	128,988	118,677	528,472	529,324	497,161
Pretax operating income, Change									35,212	21,557
Applicable taxes, Change									(11,192)	(8,610)
Net operating income, change									24,020	12,947
Realized gains (losses)-investments (after tax), Change									(20,626)	7,753
Loss on disposal of discontinued operations (after tax), Change									0	455
Acquisition expense and adjustments-Family Heritage (after tax), Change									2,436	(1,914)
Legal settlement expenses (after tax), Change									(5,931)	7,800
Guaranty Fund assessment (after tax), Change									(751)	0
State administrative settlement (after tax), Change									0	4,486
Loss on sale of equipment (after tax), Change									0	636
Net income, Change									(852)	32,163
Pretax operating income, Change %									5.00%	3.00%
Applicable taxes, Change %									5.00%	4.00%
Net operating income, Change %									5.00%	3.00%
Net income, Change %									0.00%	6.00%
Operating Segments [Member] | Life Insurance [Member]
Segment Reporting Information [Line Items]
Pretax operating income									545,059	509,476	460,963
Pretax operating income, Change									35,583	48,513
Pretax operating income, Change %									7.00%	11.00%
Operating Segments [Member] | Health Insurance [Member]
Segment Reporting Information [Line Items]
Pretax operating income									231,807	197,341	188,990
Pretax operating income, Change									34,466	8,351
Pretax operating income, Change %									17.00%	4.00%
Operating Segments [Member] | Annuity [Member]
Segment Reporting Information [Line Items]
Pretax operating income									3,939	3,465	2,345
Pretax operating income, Change									474	1,120
Pretax operating income, Change %									14.00%	48.00%
Operating Segments [Member] | Investment [Member]
Segment Reporting Information [Line Items]
Pretax operating income									218,826	236,644	258,986
Pretax operating income, Change									(17,818)	(22,342)
Pretax operating income, Change %									(8.00%)	(9.00%)
Operating Segments [Member] | Other [Member]
Segment Reporting Information [Line Items]
Pretax operating income									(176,690)	(163,507)	(156,602)
Operating Segments [Member] | Other [Member] | Other Income [Member]
Segment Reporting Information [Line Items]
Pretax operating income									2,208	1,898	2,507
Pretax operating income, Change									310	(609)
Pretax operating income, Change %									16.00%	(24.00%)
Operating Segments [Member] | Other [Member] | Administrative Expense [Member]
Segment Reporting Information [Line Items]
Pretax operating income									(178,898)	(165,405)	(159,109)
Pretax operating income, Change									(13,493)	(6,296)
Pretax operating income, Change %									8.00%	4.00%
Corporate [Member]
Segment Reporting Information [Line Items]
Pretax operating income									(34,137)	(29,827)	(22,647)
Pretax operating income, Change									$ (4,310)	$ (7,180)
Pretax operating income, Change %									14.00%	32.00%