Acquired Property Net Acquired Property Net (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Acquired Property [Roll Forward]
Acquired Property, Beginning Balance	$ 12,307	$ 11,158
Acquired Property, Additions	3,772	3,774
Acquired Property, Disposals	(3,335)	(4,213)
Acquired Property, Ending Balance	12,744	10,719
Real Estate Owned Valuation Allowance [Roll Forward]
Valuation Allowance, Beginning Balance	(686)	(669)
Valuation Allowance, Period (Increase) Decrease	(98)	99
Valuation Allowance, Ending Balance	(784)	(570)
Acquired property, net	$ 11,960	$ 10,149	$ 11,621