Principal Components of Net Deferred Tax Balances (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Income Tax [Line Items]
Future policy benefits payable	$ 246	$ 179
Net operating loss carryforward	203	181
Compensation and other accrued expenses	174	95
Benefits payable	91	111
Deferred acquisition costs	37	35
Capital loss carryforward	13	13
Unearned premiums	11	11
Other	9	20
Total deferred income tax assets	784	645
Valuation allowance	(28)	(28)
Total deferred income tax assets, net of valuation allowance	756	617
Depreciable property and intangible assets	(465)	(347)
Investment securities	(265)	(191)
Prepaid expenses	(59)	(49)
Total deferred income tax liabilities	(789)	(587)
Total net deferred income tax (liabilities) assets	(33)	30
Other long-term assets	12	46
Trade accounts payable and accrued expenses	$ (45)	$ (16)