Stock Compensation Plans (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Feb. 28, 2015	Feb. 28, 2014	Feb. 28, 2015	Feb. 28, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock based compensation expense for the period			$ 65	$ 52
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Intrinsic value for options exercised	153		226
Fair value of options vested	1		51
Cash received from the exercise of options	132		226
Tax benefit from exercise of stock options	58		85
Omnibus Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total shares authorized under Omnibus Plan (in shares)			60,400,000
Omnibus Plan [Member] | Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options granted in period (in shares)	15,458	149,684	4,117,968	6,534,762
Total stock based compensation expense for the period	34	31	65	52
Fully recognized retiree eligible expense	3	5	2	8
Grant date fair value (in dollars per share)			$ 14.64
Weighted average volatility rate (in hundredths)			25.51%
Weighted average dividend yield (in hundredths)			1.79%
Expected term			6 years 8 months 5 days
Omnibus Plan [Member] | Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options granted in period (in shares)	227,220	30,122	1,132,171	641,009
Restricted stock dividend (in shares)	16,886	19,159	37,421	40,457
Total stock based compensation expense for the period	$ 28	$ 16	$ 47	$ 26
Vesting period			3 years
Grant date fair value (in dollars per share)			$ 74.61
Omnibus Plan [Member] | Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options granted in period (in shares)	3,688	5,807	484,011	702,939
Vesting period			3 years
Grant date fair value restricted and performance shares (in dollars per share)			$ 66.82