Reconciliation Of Segment Operating Information To The Consolidated Statement Of Operations) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended			6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011		Jun. 30, 2012		Jun. 30, 2011
Segment Reporting Information [Line Items]
Premium	$ 705,582	$ 672,350	[1]	$ 1,424,057		$ 1,352,251	[1],[2]
Net investment income	175,176	173,104	[1]	349,297		344,751	[1],[2]
Other income	376	608	[1]	697		1,055	[1],[2]
Total revenue				1,774,051		1,698,057	[2]
Policy benefits	484,807	454,694	[1]	997,454		918,821	[1],[2]
Required interest on policy reserves				0		0	[2]
Required interest on deferred acquisition costs				0		0	[2]
Amortization of acquisition costs	96,601	91,664	[1]	193,099		184,127	[1],[2],[3]
Commissions, premium taxes, and non-deferred acquisition costs	50,600	55,999	[1]	101,356		111,517	[1],[2]
Insurance administrative expense				80,427	[4]	84,888	[2],[4]
Parent expense				4,210		4,811	[2]
Stock compensation expense				11,237		7,002	[2]
Interest expense	19,649	19,411	[1]	39,320		38,871	[1],[2]
Total benefits and expenses	699,415	668,282	[1]	1,427,103		1,350,037	[1],[2]
Subtotal				346,948		348,020	[2]
Nonoperating items				21,366		12,634	[2]
Amortization of low-income housing				11,164		7,441	[2]
Measure of segment profitability (pretax)				379,478		368,095	[2]
Deduct applicable income taxes				(124,209)		(121,919)	[2]
Segment profits after tax				255,269		246,176	[2]
Add back income taxes applicable to segment profitability				124,209		121,919	[2]
Add (deduct) realized investment gains (losses)	4,661	31,272	[1]	9,667		8,549	[1],[2]
Deduct Part D adjustment				(21,366)	[5]	(5,655)	[2],[5]
Deduct amortization of low-income housing				(11,164)	[6]	(7,441)	[2],[6]
Deduct estimated state administrative settlement expense						(6,000)	[2],[7]
Deduct loss on sale of equipment						(979)	[2],[8]
Income from continuing operations before income taxes	186,380	209,052	[1]	356,615		356,569	[1],[2]
Life Insurance
Segment Reporting Information [Line Items]
Premium				902,828		864,230	[2]
Total revenue				902,828		864,230	[2]
Policy benefits				583,472		556,186	[2]
Required interest on policy reserves				(238,656)		(226,155)	[2]
Required interest on deferred acquisition costs				81,814		79,152	[2]
Amortization of acquisition costs				155,649		148,004	[2]
Commissions, premium taxes, and non-deferred acquisition costs				70,254		78,901	[2]
Total benefits and expenses				652,533		636,088	[2]
Subtotal				250,295		228,142	[2]
Measure of segment profitability (pretax)				250,295		228,142	[2]
Health Insurance
Segment Reporting Information [Line Items]
Premium				509,676		475,475	[2]
Total revenue				509,676		475,475	[2]
Policy benefits				359,489		323,790	[2]
Required interest on policy reserves				(18,700)		(18,245)	[2]
Required interest on deferred acquisition costs				9,196		9,565	[2]
Amortization of acquisition costs				32,243		31,601	[2]
Commissions, premium taxes, and non-deferred acquisition costs				31,234		32,767	[2]
Total benefits and expenses				413,462		379,478	[2]
Subtotal				96,214		95,997	[2]
Measure of segment profitability (pretax)				96,214		95,997	[2]
Annuity
Segment Reporting Information [Line Items]
Premium				279		298	[2]
Total revenue				279		298	[2]
Policy benefits				21,853		20,942	[2]
Required interest on policy reserves				(29,766)		(27,705)	[2]
Required interest on deferred acquisition costs				1,177		1,339	[2]
Amortization of acquisition costs				5,207		4,522	[2]
Commissions, premium taxes, and non-deferred acquisition costs				36		34	[2]
Total benefits and expenses				(1,493)		(868)	[2]
Subtotal				1,772		1,166	[2]
Measure of segment profitability (pretax)				1,772		1,166	[2]
Investment
Segment Reporting Information [Line Items]
Net investment income				360,329		352,060	[2]
Total revenue				360,329		352,060	[2]
Required interest on policy reserves				287,122		272,105	[2]
Required interest on deferred acquisition costs				(92,187)		(90,056)	[2]
Interest expense				39,188		38,739	[2]
Total benefits and expenses				234,123		220,788	[2]
Subtotal				126,206		131,272	[2]
Measure of segment profitability (pretax)				126,206		131,272	[2]
Other & Corporate
Segment Reporting Information [Line Items]
Other income				865		1,240	[2]
Total revenue				865		1,240	[2]
Insurance administrative expense				80,427	[4]	77,909	[2],[4]
Parent expense				4,210		4,811	[2]
Stock compensation expense				11,237		7,002	[2]
Total benefits and expenses				95,874		89,722	[2]
Subtotal				(95,009)		(88,482)	[2]
Measure of segment profitability (pretax)				(95,009)		(88,482)	[2]
Adjustments
Segment Reporting Information [Line Items]
Premium				11,274	[5]	12,248	[2],[5]
Net investment income				(11,032)	[6],[9]	(7,309)	[2],[6],[9]
Other income				(168)	[10]	(185)	[10],[2]
Total revenue				74		4,754	[2]
Policy benefits				32,640	[5]	17,903	[2],[5]
Commissions, premium taxes, and non-deferred acquisition costs				(168)	[10]	(185)	[10],[2]
Insurance administrative expense						6,979	[2],[4],[7],[8]
Interest expense				132	[9]	132	[2],[9]
Total benefits and expenses				32,604		24,829	[2]
Subtotal				(32,530)		(20,075)	[2]
Nonoperating items				21,366	[5]	12,634	[2],[5],[7],[8]
Amortization of low-income housing				11,164	[6]	7,441	[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] Loss on sale of equipment.

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

[10] Elimination of intersegment commission.