Significant Accounting Policies (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2012
ASU 2010-26
Accounting pronouncements
Acquisition costs capitalized	$ 172
Acquisition costs that would have been capitalized using the previous policy	$ 177
ASU 2011-05
Accounting pronouncements
Number of separate but consecutive statements under new guidance for comprehensive income (in number of statements)	2

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