Goodwill and Other Intangible Assets - Changes During Period (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Goodwill [Roll Forward]
Balance at beginning of period	$ 47,325	$ 47,647
Changes during the period from:
Business combinations	0	8
Dispositions	(71)	(101)
Other	56	(101)
Balance at end of period	$ 47,310	$ 47,453