Acquired Property, Net (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Acquired Property [Roll Forward]
Beginning balance - Acquired property	$ 6,737	$ 10,348	$ 7,481	$ 11,442
Additions	1,648	2,431	3,485	5,366
Disposals	(2,457)	(3,580)	(5,038)	(7,609)
Ending balance - Acquired property	5,928	9,199	5,928	9,199
Valuation allowance	(428)	(693)	(428)	(693)
Ending balance - Acquired property, net	$ 5,500	$ 8,506	$ 5,500	$ 8,506	$ 6,766