Derivatives (Details) (Not designated as hedging instruments, USD $) In Millions, except Share data, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Common stock | 2014 Convertible notes
Notional amount of derivatives
Notional amount (in shares)	9,688,100	9,688,100
Interest rate lock commitments
Notional amount of derivatives
Notional	$ 4,375	$ 4,993
Forward delivery commitments
Notional amount of derivatives
Notional	11,670	12,303
Option contracts
Notional amount of derivatives
Notional	660	1,070
Interest rate contracts
Notional amount of derivatives
Notional	692	614
MSR-related agreements
Notional amount of derivatives
Notional	$ 1,565	$ 3,915