Investment Securities (Details) (USD $)	Sep. 30, 2012	Dec. 31, 2011
Schedule of Available for Sale Securities by Type
Cost	$ 5,611,000,000	$ 6,806,000,000
Gross Unrealized Gains	456,000,000	416,000,000
Gross Unrealized Losses	(7,000,000)	(75,000,000)
Estimated Fair Value	6,060,000,000	7,147,000,000
U.S. States and Political Subdivisions Debt Securities [Member]
Schedule of Available for Sale Securities by Type
Cost	4,421,000,000	4,968,000,000
Gross Unrealized Gains	199,000,000	103,000,000
Gross Unrealized Losses	(6,000,000)	(72,000,000)
Estimated Fair Value	4,614,000,000	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	374,000,000	626,000,000
Gross Unrealized Gains	7,000,000	9,000,000
Gross Unrealized Losses	(1,000,000)	(3,000,000)
Estimated Fair Value	380,000,000	632,000,000
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Schedule of Available for Sale Securities by Type
Cost	231,000,000	261,000,000
Gross Unrealized Gains	17,000,000	17,000,000
Gross Unrealized Losses	0	0
Estimated Fair Value	248,000,000	278,000,000
Equity securities [Member]
Schedule of Available for Sale Securities by Type
Cost	73,000,000	95,000,000
Gross Unrealized Gains	208,000,000	265,000,000
Gross Unrealized Losses	0	0
Estimated Fair Value	281,000,000	360,000,000
Foreign government bonds and obligations [Member]
Schedule of Available for Sale Securities by Type
Cost	126,000,000	120,000,000
Gross Unrealized Gains	15,000,000	10,000,000
Gross Unrealized Losses	0	0
Estimated Fair Value	141,000,000	130,000,000
Available For Sale Securities Other [Member]
Schedule of Available for Sale Securities by Type
Cost	53,000,000	54,000,000
Gross Unrealized Gains	1,000,000	0
Gross Unrealized Losses	0	0
Estimated Fair Value	$ 54,000,000	$ 54,000,000

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

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

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

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

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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