Deferred Policy Acquisition Costs And Insurance Expenses - Additional Information (Detail) (USD $) In Billions, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Deferred Policy Acquisition Costs And Insurance Expenses [Line Items]
Consolidated policy acquisition costs deferred	$ 1.68	$ 1.44	$ 1.30
Commissions deferred as a percentage of total acquisition costs	77.00%	77.00%	76.00%
Personnel, compensation and benefit expenses as a percentage of insurance expenses	42.00%	44.00%	43.00%

Total amount of policy acquisition costs capitalized during the income statement period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 30

-Section 50

-Paragraph 1

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6967983&loc=d3e11264-158415

Name:	us-gaap_DeferredPolicyAcquisitionCostsAdditions
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration