Reconciliation of Segment Operating Information to Consolidated Statement of Operations (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011		Mar. 31, 2011	Sep. 30, 2012		Sep. 30, 2011
Segment Reporting Information [Line Items]
Premium	$ 699,860	$ 650,525	[1]		$ 2,123,917		$ 2,002,776	[1],[2]
Net investment income	169,400	173,491	[1]		518,697		518,242	[1],[2]
Other income	557	625	[1]		1,254		1,680	[1],[2]
Total revenue					2,643,868		2,522,698	[2]
Policy benefits	479,119	438,774	[1]		1,476,573		1,357,595	[1],[2]
Policy reserves					0		0	[2]
Deferred acquisition costs					0		0	[2]
Amortization of acquisition costs	94,016	89,899	[1]		287,115		274,026	[1],[2],[3]
Commissions, premium taxes, and non-deferred acquisition costs	46,898	53,667	[1]		148,254		165,184	[1],[2]
Insurance administrative expense					120,942	[4]	124,775	[2],[4]
Parent expense					6,818		6,162	[2]
Stock compensation expense					16,547		11,032	[2]
Interest expense	19,843	19,510	[1]		59,163		58,381	[1],[2]
Total benefits and expenses	688,309	647,118	[1]		2,115,412		1,997,155	[1],[2]
Subtotal					528,456		525,543	[2]
Nonoperating items					19,537		12,816	[2]
Amortization of low-income housing					16,826		10,858	[2]
Measure of segment profitability (pretax)					564,819		549,217	[2]
Deduct applicable income taxes					(184,800)		(179,857)	[2]
Segment profits after tax					380,019		369,360	[2]
Add back income taxes applicable to segment profitability					184,800		179,857	[2]
Add (deduct) realized investment gains (losses)	7,283	12,600	[1]		16,950		21,149	[1],[2]
Deduct Part D adjustment					(18,922)	[5]	(5,837)	[2],[5]
Deduct amortization of low-income housing					(16,826)	[6]	(10,858)	[2],[6]
Deduct estimated state administrative settlement expense							(6,000)	[2],[7]
Deduct Family Heritage Life acquisition expense					(615)	[8]
Deduct loss on sale of equipment				(979)			(979)	[2],[9]
Pretax income from continuing operations per Consolidated Statement of Operations	188,791	190,123	[1]		545,406		546,692	[1],[2]
Life Insurance
Segment Reporting Information [Line Items]
Premium					1,356,527		1,294,157	[2]
Total revenue					1,356,527		1,294,157	[2]
Policy benefits					879,317		836,358	[2]
Policy reserves					(360,454)		(341,452)	[2]
Deferred acquisition costs					122,453		119,364	[2]
Amortization of acquisition costs					231,926		220,269	[2]
Commissions, premium taxes, and non-deferred acquisition costs					102,696		116,406	[2]
Total benefits and expenses					975,938		950,945	[2]
Subtotal					380,589		343,212	[2]
Measure of segment profitability (pretax)					380,589		343,212	[2]
Health Insurance
Segment Reporting Information [Line Items]
Premium					760,825		702,807	[2]
Total revenue					760,825		702,807	[2]
Policy benefits					539,212		478,392	[2]
Policy reserves					(28,242)		(27,521)	[2]
Deferred acquisition costs					13,710		14,221	[2]
Amortization of acquisition costs					47,536		46,722	[2]
Commissions, premium taxes, and non-deferred acquisition costs					45,752		48,998	[2]
Total benefits and expenses					617,968		560,812	[2]
Subtotal					142,857		141,995	[2]
Measure of segment profitability (pretax)					142,857		141,995	[2]
Annuity
Segment Reporting Information [Line Items]
Premium					440		438	[2]
Total revenue					440		438	[2]
Policy benefits					32,997		31,634	[2]
Policy reserves					(44,690)		(42,139)	[2]
Deferred acquisition costs					1,721		1,990	[2]
Amortization of acquisition costs					7,653		7,035	[2]
Commissions, premium taxes, and non-deferred acquisition costs					53		53	[2]
Total benefits and expenses					(2,266)		(1,427)	[2]
Subtotal					2,706		1,865	[2]
Measure of segment profitability (pretax)					2,706		1,865	[2]
Investment
Segment Reporting Information [Line Items]
Net investment income					535,325		528,902	[2]
Total revenue					535,325		528,902	[2]
Policy reserves					433,386		411,112	[2]
Deferred acquisition costs					(137,884)		(135,575)	[2]
Interest expense					58,965		58,183	[2]
Total benefits and expenses					354,467		333,720	[2]
Subtotal					180,858		195,182	[2]
Measure of segment profitability (pretax)					180,858		195,182	[2]
Other & Corporate
Segment Reporting Information [Line Items]
Other income					1,501		1,953	[2]
Total revenue					1,501		1,953	[2]
Insurance administrative expense					120,942	[4]	117,796	[2],[4]
Parent expense					6,203		6,162	[2]
Stock compensation expense					16,547		11,032	[2]
Total benefits and expenses					143,692		134,990	[2]
Subtotal					(142,191)		(133,037)	[2]
Measure of segment profitability (pretax)					(142,191)		(133,037)	[2]
Adjustments
Segment Reporting Information [Line Items]
Premium					6,125	[5]	5,374	[2],[5]
Net investment income					(16,628)	[10],[6]	(10,660)	[10],[2],[6]
Other income					(247)	[11]	(273)	[11],[2]
Total revenue					(10,750)		(5,559)	[2]
Policy benefits					25,047	[5]	11,211	[2],[5]
Commissions, premium taxes, and non-deferred acquisition costs					(247)	[11]	(273)	[11],[2]
Insurance administrative expense							6,979	[2],[4],[7],[9]
Parent expense					615	[8]
Interest expense					198	[10]	198	[10],[2]
Total benefits and expenses					25,613		18,115	[2]
Subtotal					(36,363)		(23,674)	[2]
Nonoperating items					19,537	[5],[8]	12,816	[2],[5],[7],[9]
Amortization of low-income housing					16,826	[6]	10,858	[2],[6]
Measure of segment profitability (pretax)					$ 0		$ 0	[2]

[1] The 2011 balances have been retrospectively adjusted to give effect to the adoption of new accounting guidance as described in Note F-Adoption of New Accounting Standard.

[2] The 2011 balances have been retroactively adjusted to give effect to the adoption of new accounting guidance as described in Note F-Adoption of New Accounting Standard.

[3] The 2011 balances have been retroactively adjusted to give effect to the adoption of the new accounting guidance.

[4] Administrative expense is not allocated to insurance segments.

[5] Medicare Part D items adjusted to GAAP from the segment analysis, which matches expected benefits with policy premium.

[6] Amortization of low-income housing expense, considered a component of income tax expense in the segment analysis.

[7] Estimated state administrative settlement expense.

[8] Family Heritage Life acquisition expense.

[9] Loss on sale of equipment.

[10] Reclassification of interest amount due to accounting rule requiring deconsolidation of Trust Preferred Securities. Management views the Trust Preferreds as consolidated debt.

[11] Elimination of intersegment commission.