1) For defined benefit pension plans, the benefit obligation is the projected benefit obligation, which is the actuarial present value as of a date of all benefits attributed by the pension benefit formula to employee service rendered prior to that date. 2) For other postretirement defined benefit plans, the benefit obligation is the accumulated postretirement benefit obligation, which is the actuarial present value of benefits attributed to employee service rendered to a particular date.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Retirement benefits - additional information (Details) - USD ($) $ in Millions	3 Months Ended	8 Months Ended	12 Months Ended
	May 31, 2017	Aug. 31, 2015	Aug. 31, 2017	Aug. 31, 2016	Aug. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Defined benefit pension plan, investments holding percentage			85.00%
Cash contributions to defined benefit pension plans			$ 54
Profit sharing provision expense			221	$ 226	$ 158
Contributions to profit sharing			220	225	$ 249
Cost recognized in the consolidated condensed statements of earnings		$ 93	112	130
Postretirement Health Benefit Plan
Defined Benefit Plan Disclosure [Line Items]
Curtailment gain	$ 109
Defined benefit plan obligation			361	$ 466
Expected benefit to be paid net of estimated federal subsidy during fiscal year 2017			$ 10