Investments in Securities Other-than-temporary Impairments 3 (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Noncredit portion of other-than-temporary impairments recognized in the other comprehensive income	$ 33	$ 16
Available-for-sale Securities [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Balance, beginning of period	9,214	8,915
Additions for the credit component on debt securities for which OTTI was not previously recognized	5	0
Additions for the credit component on debt securities for which OTTI was previously recognized	4	64
Reductions for securities no longer in portfolio at period end	(2)	0
Reductions for amortization resulting from changes in cash flows expected to be collected over the remaining life of the securities	(85)	(109)
Balance, end of period	$ 9,136	$ 8,870