Investment Securities (Details) (USD $)	Jun. 30, 2012	Dec. 31, 2011
Schedule of Available for Sale Securities by Type
Cost	$ 5,939,000,000	$ 6,806,000,000
Gross Unrealized Gains	410,000,000	416,000,000
Gross Unrealized Losses	(23,000,000)	(75,000,000)
Estimated Fair Value	6,326,000,000	7,147,000,000
U.S. States and Political Subdivisions Debt Securities [Member]
Schedule of Available for Sale Securities by Type
Cost	4,643,000,000	4,968,000,000
Gross Unrealized Gains	157,000,000	103,000,000
Gross Unrealized Losses	(21,000,000)	(72,000,000)
Estimated Fair Value	4,779,000,000	4,999,000,000
U.S. Government agency obligations [Member]
Schedule of Available for Sale Securities by Type
Cost	3,000,000	352,000,000
Gross Unrealized Gains	0	2,000,000
Gross Unrealized Losses	0	0
Estimated Fair Value	3,000,000	354,000,000
U.S. Government treasury obligations [Member]
Schedule of Available for Sale Securities by Type
Cost	330,000,000	330,000,000
Gross Unrealized Gains	9,000,000	10,000,000
Gross Unrealized Losses	0	0
Estimated Fair Value	339,000,000	340,000,000
Corporate debt securities [Member]
Schedule of Available for Sale Securities by Type
Cost	471,000,000	626,000,000
Gross Unrealized Gains	5,000,000	9,000,000
Gross Unrealized Losses	(2,000,000)	(3,000,000)
Estimated Fair Value	474,000,000	632,000,000
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Schedule of Available for Sale Securities by Type
Cost	241,000,000	261,000,000
Gross Unrealized Gains	17,000,000	17,000,000
Gross Unrealized Losses	0	0
Estimated Fair Value	258,000,000	278,000,000
Equity securities [Member]
Schedule of Available for Sale Securities by Type
Cost	81,000,000	95,000,000
Gross Unrealized Gains	209,000,000	265,000,000
Gross Unrealized Losses	0	0
Estimated Fair Value	290,000,000	360,000,000
Foreign government bonds and obligations [Member]
Schedule of Available for Sale Securities by Type
Cost	118,000,000	120,000,000
Gross Unrealized Gains	12,000,000	10,000,000
Gross Unrealized Losses	0	0
Estimated Fair Value	130,000,000	130,000,000
Availabe For Sale Securities Other [Member]
Schedule of Available for Sale Securities by Type
Cost	52,000,000	54,000,000
Gross Unrealized Gains	1,000,000	0
Gross Unrealized Losses	0	0
Estimated Fair Value	$ 53,000,000	$ 54,000,000

For an unclassified balance sheet, this item represents investments in debt and equity securities which are categorized neither as held-to-maturity nor trading.

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-Publisher FASB

-Name Accounting Standards Codification

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-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.

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Reference 4: http://www.xbrl.org/2003/role/presentationRef

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-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.

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Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

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-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 7: http://www.xbrl.org/2003/role/presentationRef

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Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

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-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 9: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 16

-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.

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-Section 25

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+ Details

- Definition

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References+ Details

- Definition

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.

+ References+ Details