Credit Risk (Details 1) (USD $) In Millions	6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010
Summary of the activity in foreclosure-related reserves
Balance, beginning of period	$ 111	$ 86
Realized foreclosure losses	(35)	(32)
Increase in reserves due to:
Changes in assumptions	39	45
New loan sales	7	5
Balance, end of period	$ 122	$ 104