Equity Method Investments (Details) shares in Millions, $ in Millions, £ in Billions				12 Months Ended
		Dec. 31, 2014 shares	Aug. 02, 2012 USD ($) shares	Aug. 31, 2015 USD ($)	Aug. 31, 2014 USD ($)	Aug. 31, 2013 USD ($)	Aug. 02, 2012 GBP (£)
Schedule of Equity Method Investments [Line Items]
Remaining ownership subject to call option					55.00%
Shares issued upon exercise of call option (in shares) | shares		144.3
Non-controlling interests				$ 163	$ 283
Equity earnings	[1]			339	$ 618	$ 496
Alliance Boots [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment ownership interest percentage		45.00%	45.00%		45.00%		45.00%
Cash paid to acquire investment			$ 4,025
Shares issued for Investment in Alliance Boots (in shares) | shares			83.4
Remaining ownership subject to call option			55.00%				55.00%
Cash price to exercise call option | £							£ 3.1
Shares issued upon exercise of call option (in shares) | shares			144.3
Equity method investments investment amount			$ 2,400
Incremental acquisition related amortization				14	$ 41	68
Non-cash gain resulting from the remeasurement of previously held equity interest				563
Foreign currency translation gains and losses recycled from cumulative other comprehensive income				310
Equity earnings					$ 617	$ 496
Other Equity Method Investments [Member]
Schedule of Equity Method Investments [Line Items]
Equity earnings				$ 24

[1] Earnings in foreign equity method investments are translated at their respective average exchange rates.