Debt - narrative (Details)	12 Months Ended
	Aug. 31, 2020 USD ($)	Aug. 31, 2019 USD ($)	Aug. 31, 2018 USD ($)	May 29, 2020 USD ($)	Apr. 15, 2020 USD ($)	Apr. 07, 2020 USD ($)	Apr. 02, 2020 USD ($)	Apr. 01, 2020 USD ($)	Aug. 30, 2019 USD ($) credit_agreement	Jan. 18, 2019 USD ($)	Dec. 21, 2018 USD ($)	Dec. 05, 2018 USD ($)	Aug. 29, 2018 USD ($)
Line of Credit Facility [Line Items]
Interest paid, net of capitalized interest	$ 584,000,000	$ 676,000,000	$ 577,000,000
Commercial Paper
Line of Credit Facility [Line Items]
Average daily short-term borrowings	$ 2,500,000,000	$ 2,700,000,000
Weighted-average interest rate	2.15%	3.07%
Maximum
Line of Credit Facility [Line Items]
Debt to total capitalization ratio	0.60
2018 Revolving Credit Agreement
Line of Credit Facility [Line Items]
Borrowings outstanding	$ 0
Total $1.5 billion debt issuance
Line of Credit Facility [Line Items]
Face amount					$ 1,500,000,000
Underwriting discounts and estimated offering expenses	13,300,000
Line of Credit | November 2018 Credit Agreement
Line of Credit Facility [Line Items]
Borrowings outstanding	1,000,000,000.0
Unsecured Debt | December 2018 Term Loan Credit Agreement
Line of Credit Facility [Line Items]
Face amount												$ 1,000,000,000.0
Unsecured Debt | Total $1.5 billion debt issuance
Line of Credit Facility [Line Items]
Face amount	$ 1,500,000,000
Unsecured Debt | 3.200% unsecured notes due 2030
Line of Credit Facility [Line Items]
Face amount					$ 500,000,000
Stated interest rate (as a percent)	3.20%				3.20%
Unsecured Debt | 4.100% unsecured notes due 2050
Line of Credit Facility [Line Items]
Face amount					$ 1,000,000,000.0
Stated interest rate (as a percent)	4.10%				4.10%
Revolving Credit Facility | August 2019 Revolving Credit Agreements
Line of Credit Facility [Line Items]
Maximum borrowing capacity									$ 500,000,000
Borrowings outstanding	$ 0
Number of credit agreements | credit_agreement									3
Revolving Credit Facility | January 2019 364-Day Revolving Credit Agreement
Line of Credit Facility [Line Items]
Maximum borrowing capacity										$ 2,000,000,000.0
Borrowings outstanding	0
Revolving Credit Facility | December 2018 Revolving Credit Agreement
Line of Credit Facility [Line Items]
Maximum borrowing capacity											$ 1,000,000,000.0
Revolving Credit Facility | 2018 Revolving Credit Agreement
Line of Credit Facility [Line Items]
Face amount													$ 3,500,000,000
Revolving Credit Facility | April 7, 2020 Revolving Credit Agreement
Line of Credit Facility [Line Items]
Maximum borrowing capacity						$ 500,000,000
Borrowings outstanding	0
Revolving Credit Facility | April 2020 Revolving Bilateral Credit Agreement
Line of Credit Facility [Line Items]
Maximum borrowing capacity								$ 750,000,000
Revolving Credit Facility | April 2020 Revolving Club Credit Agreement
Line of Credit Facility [Line Items]
Maximum borrowing capacity							$ 1,325,000,000
Revolving Credit Facility | Other April 2020 Revolving Credit Agreement
Line of Credit Facility [Line Items]
Borrowings outstanding	0
Revolving Credit Facility | A&R December 2018 Credit Agreement
Line of Credit Facility [Line Items]
Face amount							2,000,000,000.0
Revolving Credit Facility | Line of Credit | November 2018 Credit Agreement
Line of Credit Facility [Line Items]
Maximum borrowing capacity				$ 500,000,000
Revolving Credit Facility | Unsecured Debt | November 2018 Credit Agreement
Line of Credit Facility [Line Items]
Maximum borrowing capacity				$ 1,000,000,000.0
Revolving Credit Facility | Unsecured Debt | A&R December 2018 Credit Agreement
Line of Credit Facility [Line Items]
Face amount							$ 1,000,000,000.0
Loans Payable | December 2018 Term Loan Credit Agreement
Line of Credit Facility [Line Items]
Borrowings outstanding	$ 100,000,000
Letter of Credit | 2018 Revolving Credit Agreement
Line of Credit Facility [Line Items]
Face amount													$ 500,000,000