Fair Value of Assets and Liabilities (Changes in Fair Values Recorded in Earnings for FVO Assets-Liabilities (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Other Long-term Investments [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)	$ 40	$ (5)	$ 18
Commercial Mortgage Loans [Member]
Changes in instrument-specific credit risk	0	1	6
Other changes in fair value	(1)	4	3
Notes Issued By Consolidated V I E [Member]
Fair Value, Option, Changes in Fair Value, Gain (Loss)	$ 2	$ 0	$ 0

This item represents the estimated amount of gains or losses included in earnings during the period attributable to changes in instrument-specific credit risk arising from loans and other receivables held as assets.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 30

-Subparagraph (c)(1)

-URI http://asc.fasb.org/extlink&oid=6957238&loc=d3e14172-108612

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 159

-Paragraph 19

-Subparagraph c(1)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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_FairValueOptionCreditRiskGainsLossesOnAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration