Identifiable Assets (Detail) (USD $) In Millions	Jun. 30, 2011	Dec. 31, 2010
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ 15,702	$ 15,095
Property, Liability and Casualty Insurance Segment
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	2,336	2,008
Life Insurance Segment
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	1,252	1,214
Investments Segment
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	11,814	11,543
Other
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ 300	$ 330