Changes in Liability for Unpaid Policy Claims (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Less claims paid during the year on claims incurred during:
Total liability for unpaid policy claims	$ 3,981	$ 3,719	$ 3,270
Health insurance
Liability for Future Policy Benefit, by Product Segment [Line Items]
Unpaid supplemental health claims, beginning of year	3,524	3,105	2,959
Add claims incurred during the year related to:
Current year	7,703	7,262	6,864
Prior years	(256)	(332)	(398)
Total incurred	7,447	6,930	6,466
Less claims paid during the year on claims incurred during:
Current year	5,401	5,003	4,683
Prior years	1,944	1,787	1,618
Total paid	7,345	6,790	6,301
Effect of foreign exchange rate changes on unpaid claims	123	279	(19)
Total liability for unpaid policy claims	3,749	3,524	3,105
Life insurance
Less claims paid during the year on claims incurred during:
Total liability for unpaid policy claims	$ 232	$ 195	$ 165