Acquired Property Net (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011
Acquired Property [Roll Forward]
Acquired Property, Beginning Balance	$ 11,035		$ 14,915		$ 12,401		$ 18,054
Acquired Property, Additions	4,349		4,066		12,457		13,953
Acquired Property, Disposals	(4,442)		(5,606)		(13,916)		(18,632)
Acquired Property, Ending Balance	10,942		13,375		10,942		13,375
Valuation Allowance [Roll Forward]
Valuation Allowance, Beginning Balance	(648)	[1]	(1,323)	[1]	(1,028)	[1]	(1,881)	[1]
Valuation Allowance, Additions	(259)	[1]	(144)	[1]	(500)	[1]	(422)	[1]
Valuation Allowance, Disposals	298	[1]	601	[1]	1,211	[1]	2,119	[1]
Valuation Allowance, Write-downs, net of recoveries	(55)	[1]	(314)	[1]	(347)	[1]	(996)	[1]
Valuation Allowance, Ending Balance	(664)	[1]	(1,180)	[1]	(664)	[1]	(1,180)	[1]
Acquired Property, Net [Roll Forward]
Acquired Property, Net Beginning Balance	10,387		13,592		11,373		16,173
Acquired Property, Net Additions	4,090		3,922		11,957		13,531
Acquired Property, Net Disposals	(4,144)		(5,005)		(12,705)		(16,513)
Valuation Allowance, Write-downs, net of recoveries	(55)	[1]	(314)	[1]	(347)	[1]	(996)	[1]
Acquired Property, Net Ending Balance	$ 10,278		$ 12,195		$ 10,278		$ 12,195

[1] Reflects activities in the valuation allowance for acquired properties held primarily by our single-family segment.