Business Segments - Analysis of Profitability by Segment (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Segment Reporting Information [Line Items]
Pretax operating income			$ 405,315	$ 392,947
Applicable taxes			(132,458)	(128,632)
Net operating income			272,857	264,315
Realized gains (losses)-Investments			11,177	76
Part D adjustment			(16,749)	(9,782)
Guaranty Fund assessment			0	(751)
Administrative settlements			(1,987)	0
Legal settlement expense			(1,519)	(325)
Net income	130,923	133,901	263,779	253,533
Applicable taxes, Increase (Decrease)			(3,826)
Net operating income, Increase (Decrease)			8,542
Realized gains (losses) - Investments net of tax, Increase (Decrease)			11,101
Part D adjustment net of tax, Increase (Decrease)			(6,967)
Guaranty Fund assessment, Increase (Decrease)			751
Administrative settlements, Increase (Decrease)			(1,987)
Legal settlement expenses net of tax, Increase (Decrease)			(1,194)
Net income, Increase (Decrease)			10,246
Pretax operating income, Increase (Decrease) %			3.00%
Applicable taxes, Change %			3.00%
Net operating income, Change %			3.00%
Net income, Change %			4.00%
Medicare Part D [Member]
Segment Reporting Information [Line Items]
Part D adjustment			(16,749)	(9,782)
Operating Segments [Member]
Segment Reporting Information [Line Items]
Pretax operating income, Change			12,368
Operating Segments [Member] | Life Insurance [Member]
Segment Reporting Information [Line Items]
Pretax operating income			281,335	268,840
Pretax operating income, Change			12,495
Pretax operating income, Increase (Decrease) %			5.00%
Operating Segments [Member] | Health Insurance [Member]
Segment Reporting Information [Line Items]
Pretax operating income			99,245	100,124
Pretax operating income, Change			(879)
Pretax operating income, Increase (Decrease) %			(1.00%)
Operating Segments [Member] | Medicare Part D [Member]
Segment Reporting Information [Line Items]
Pretax operating income			18,211	16,236
Pretax operating income, Change			1,975
Pretax operating income, Increase (Decrease) %			12.00%
Operating Segments [Member] | Annuity [Member]
Segment Reporting Information [Line Items]
Pretax operating income			2,110	1,996
Pretax operating income, Change			114
Pretax operating income, Increase (Decrease) %
Operating Segments [Member] | Investment [Member]
Segment Reporting Information [Line Items]
Pretax operating income			114,167	110,469
Pretax operating income, Change			3,698
Pretax operating income, Increase (Decrease) %			3.00%
Operating Segments [Member] | Other and Corporate [Member]
Segment Reporting Information [Line Items]
Pretax operating income			(109,753)	(104,718)
Operating Segments [Member] | Other and Corporate [Member] | Other Income [Member]
Segment Reporting Information [Line Items]
Pretax operating income			1,266	1,227
Pretax operating income, Change			39
Pretax operating income, Increase (Decrease) %			3.00%
Operating Segments [Member] | Other and Corporate [Member] | Administrative Expense [Member]
Segment Reporting Information [Line Items]
Pretax operating income			(89,573)	(88,062)
Pretax operating income, Change			(1,511)
Pretax operating income, Increase (Decrease) %			2.00%
Operating Segments [Member] | Other and Corporate [Member] | Corporate [Member]
Segment Reporting Information [Line Items]
Pretax operating income			(21,446)	(17,883)
Pretax operating income, Change			$ (3,563)
Pretax operating income, Increase (Decrease) %			20.00%