Financial Instruments, Unrealized Gains on Available For Sale Securities (Details) (USD $) In Millions	Sep. 30, 2011 Available For Sale Securities	Dec. 31, 2010 Available For Sale Securities
Available For Sale Securities: Special Use Funds - Equity Securities [Member]
Available For Sale Securities Gross Unrealized Gains Abstract
Unrealized gains	$ 372	$ 612
Available For Sale Securities: Special Use Funds - U.S. Government And Municipal Bonds [Member]
Available For Sale Securities Gross Unrealized Gains Abstract
Unrealized gains	48	15
Available For Sale Securities: Special Use Funds - Corporate Debt Securities [Member]
Available For Sale Securities Gross Unrealized Gains Abstract
Unrealized gains	28	23
Available For Sale Securities: Special Use Funds - Mortgage-Backed Securities [Member]
Available For Sale Securities Gross Unrealized Gains Abstract
Unrealized gains	27	20
Available For Sale Securities: Special Use Funds - Other Debt Securities [Member]
Available For Sale Securities Gross Unrealized Gains Abstract
Unrealized gains	$ 3	$ 2

This item represents the gross unrealized gains for securities, at a point in time, which are categorized neither as held-to-maturity nor trading securities.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 22

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 13, 19

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27161-111563

Name:	us-gaap_AvailableforsaleSecuritiesGrossUnrealizedGain
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant