Share-based Compensation - Restricted Stock Units ("RSUs") - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
Aug. 31, 2020	Aug. 31, 2019	Aug. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock unit expense	$ 4	$ 6	$ 7
Restricted stock units (“RSUs”)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares)	470,917	261,642	252,865
Vesting percentage per year	20.00%
Vesting term	5 years
Shares granted, fair value	$ 7	$ 7	$ 7
Weighted average grant date fair value, granted	$ 14.88	$ 27.61	$ 26.60
Total fair value of shares vested during period	$ 6	$ 7	$ 8
Compensation cost not yet recognized	$ 10
Compensation cost not yet recognized, period for recognition	3 years
Restricted stock units (“RSUs”) \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period for retirement eligibility for expense to be recognized	5 years
Restricted stock units (“RSUs”) \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period for retirement eligibility for expense to be recognized	2 years
Restricted stock units (“RSUs”) \| Class A Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares entitled to be received upon vesting	1

Number of shares entitled to be received upon vesting.

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- Definition

Share based compensation arrangement by share based payment award equity instruments other than options grants in period fair value.

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- Definition

Share based compensation expense recognition period for participants who were or will become retirement eligible during the award term.

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

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-Publisher FASB
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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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Amount of noncash expense for award of restricted stock or unit under share-based payment arrangement.

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Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

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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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- Definition

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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- Definition

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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Percentage of vesting of award under share-based payment arrangement.

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