Supplemental Information Concerning Property-Casualty Insurance Operations (Details Textual) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Supplemental Information for Property, Casualty Insurance Underwriters [Abstract]
Reinsurance recoverables	$ 2,716	$ 2,238	$ 2,249
Supplemental information concerning property-casualty insurance operations, discounted rate	4.50%	6.00%
Prepaid reinsurance premiums	$ 471	$ 409

The unexpired portion of premiums ceded on policies in force as of the balance sheet date.

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Prepaid Reinsurance Premiums

-URI http://asc.fasb.org/extlink&oid=6521719

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 340

-Section 25

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6485982&loc=d3e22818-158507

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 113

-Paragraph 14, 27, 28

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Name:	us-gaap_PrepaidReinsurancePremiums
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant