Fair Value (Details 4) (USD $) In Millions	Sep. 30, 2011	Dec. 31, 2010
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying value at estimated fair value	$ 59,209	$ 58,976
Variable interest entities | Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unpaid principal balance	3,063	6,636
Excess estimated fair value over unpaid principal balance	164	204
Carrying value at estimated fair value	3,227	6,840
Variable interest entities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying value at estimated fair value	$ 3,277	$ 6,840