Investment Securities (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Schedule of Available for Sale Securities by Type
Cost	$ 5,063	$ 5,145
Gross Unrealized Gains	244	474
Gross Unrealized Losses	(45)	(5)
Estimated Fair Value	5,262	5,614
U.S. States and Political Subdivisions Debt Securities [Member]
Schedule of Available for Sale Securities by Type
Cost	4,351	4,280
Gross Unrealized Gains	81	199
Gross Unrealized Losses	(43)	(5)
Estimated Fair Value	4,389	4,474
U.S. Government agency obligations [Member]
Schedule of Available for Sale Securities by Type
Cost	3	3
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	3	3
U.S. Government treasury obligations [Member]
Schedule of Available for Sale Securities by Type
Cost	280	330
Gross Unrealized Gains	5	8
Gross Unrealized Losses	0	0
Estimated Fair Value	285	338
Corporate debt securities [Member]
Schedule of Available for Sale Securities by Type
Cost	40	73
Gross Unrealized Gains	3	6
Gross Unrealized Losses	0	0
Estimated Fair Value	43	79
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Schedule of Available for Sale Securities by Type
Cost	170	210
Gross Unrealized Gains	6	14
Gross Unrealized Losses	0	0
Estimated Fair Value	176	224
Equity securities [Member]
Schedule of Available for Sale Securities by Type
Cost	46	64
Gross Unrealized Gains	143	232
Gross Unrealized Losses	0	0
Estimated Fair Value	189	296
Foreign government bonds and obligations [Member]
Schedule of Available for Sale Securities by Type
Cost	122	134
Gross Unrealized Gains	6	15
Gross Unrealized Losses	(1)	0
Estimated Fair Value	127	149
Availabe For Sale Securities Other [Member]
Schedule of Available for Sale Securities by Type
Cost	51	51
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1)	0
Estimated Fair Value	$ 50	$ 51

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 45

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-Publisher FASB

-Name Accounting Standards Codification

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 12

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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 4: 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 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 13

-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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

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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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-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

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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 FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 15E

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

-Publisher FASB

-Name FASB Staff Position (FSP)

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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.

+ 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