Goodwill (Details) (USD $)	6 Months Ended
	Jun. 30, 2014
Goodwill [Roll Forward]
Balance, December 31, 2013	$ 26,542,000,000
Acquisitions	1,576,000,000
Foreign currency translation adjustments	9,000,000
Other	(1,000,000)	[1]
Balance, June 30, 2014	28,126,000,000
Pharmacy Services Segment
Goodwill [Roll Forward]
Balance, December 31, 2013	19,658,000,000
Acquisitions	1,576,000,000
Foreign currency translation adjustments	0
Other	(1,000,000)	[1]
Balance, June 30, 2014	21,233,000,000
Retail Pharmacy Segment
Goodwill [Roll Forward]
Balance, December 31, 2013	6,884,000,000
Acquisitions	0
Foreign currency translation adjustments	9,000,000
Other	0	[1]
Balance, June 30, 2014	$ 6,893,000,000

[1] "Other" represents immaterial purchase accounting adjustments for acquisitions.