Share-based Compensation - Performance Share Awards - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
Aug. 31, 2021	Aug. 31, 2020	Aug. 31, 2019
Performance Shares (PSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, award requisite service period	3 years	3 years	3 years
Shares granted (in shares)	316,649	337,770	254,620
Weighted average grant date fair value, granted	$ 22.33	$ 21.32	$ 28.37
Share vested	$ 7	$ 10	$ 13
Compensation cost not yet recognized	$ 11
Compensation cost not yet recognized, period for recognition	2 years
Performance Shares (PSUs) \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance based awards award payouts threshold	50.00%
Performance Shares (PSUs) \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance based awards award payouts threshold	200.00%
Total Shareholder Return (TSR)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 3	$ 3	$ 4
Shares granted (in shares)	157,791	165,834	123,812
Return on Capital Employed Awards and Other Performance Share Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 7	$ 2	$ 6
Return on Capital Employed Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares)	158,858	171,936	130,808

Performance based awards award payouts threshold.

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Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Estimated period over which an employee is required to provide service in exchange for the equity-based payment award, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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