Equity Method Investments (Details) In Millions, unless otherwise specified	0 Months Ended	3 Months Ended				6 Months Ended					0 Months Ended		3 Months Ended		6 Months Ended					3 Months Ended	6 Months Ended
	Dec. 31, 2014	Feb. 28, 2015 USD ($)		Feb. 28, 2014 USD ($)		Feb. 28, 2015 USD ($)		Feb. 28, 2014 USD ($)		Aug. 31, 2014 USD ($)	Dec. 31, 2014 Alliance Boots [Member]	Jun. 18, 2012 Alliance Boots [Member] USD ($)	Feb. 28, 2015 Alliance Boots [Member] USD ($)	Feb. 28, 2014 Alliance Boots [Member] USD ($)	Feb. 28, 2015 Alliance Boots [Member] USD ($)	Feb. 28, 2014 Alliance Boots [Member] USD ($)	Feb. 28, 2015 Alliance Boots [Member] GBP (£)	Dec. 31, 2014 Alliance Boots [Member]	Aug. 31, 2014 Alliance Boots [Member]	Feb. 28, 2015 Other Equity Method Investments [Member] USD ($)	Feb. 28, 2015 Other Equity Method Investments [Member] USD ($)
Schedule of Equity Method Investments [Line Items]
Equity interest in Alliance Boots (in hundredths)		45.00%				45.00%						45.00%	100.00%		100.00%			45.00%	45.00%
Cash paid to acquire investment												$ 4,025
Shares issued for Investment in Alliance Boots (in shares)												83.4
Remaining ownership subject to call option (in hundredths)														55.00%		55.00%
Cash price to exercise call option																	3,100
Shares issued upon exercise of call option (in shares)	144.3										144.3
Equity method investments investment amount												2,400
Non-controlling interests		151				151				283
Incremental acquisition related amortization													4	10	14	20
Incremental acquisition related amortization, net of tax													3	8	8	16
Non-cash gain resulting from the remeasurement of previously held equity interest															706
Foreign currency translation gains and losses recycled from cumulative other comprehensive income													80		80
Equity earnings		$ 109	[1]	$ 136	[1]	$ 323	[1]	$ 330	[1]											$ 8	$ 8

[1] Alliance Boots became a consolidated subsidiary and ceased being accounted for under the equity method upon completion of the Second Step Transaction on December 31, 2014. Earnings for the quarter and six month periods ended February 28, 2015 reflect incremental acquisition-related amortization expense of $4 million ($3 million net of tax) and $14 million ($8 million net of tax), respectively. Incremental acquisition-related amortization for the three and six month periods ended February 28, 2014 were $10 million ($8 million net of tax) and $20 million ($16 million net of tax), respectively. Earnings in foreign equity method investments and joint ventures are translated at the average exchange rates of $1.56 and $1.58 to one British Pound Sterling for the quarter and six month periods ended February 28, 2015, respectively. Prior year's earnings in foreign equity method investments and joint ventures were translated at the average exchange rate of $1.64 and $1.62 to one British Pound Sterling for the quarter and six month periods ended February 28, 2014, respectively.