Debt - narrative (Details)	12 Months Ended
	Aug. 31, 2019 USD ($)	Aug. 31, 2018 USD ($)	Aug. 31, 2017 USD ($)	Aug. 30, 2019 USD ($)	Jan. 18, 2019 USD ($)	Dec. 21, 2018 USD ($)	Dec. 05, 2018 USD ($)	Nov. 30, 2018 USD ($)	Aug. 29, 2018 USD ($)	Aug. 24, 2017 USD ($)	Feb. 01, 2017 USD ($)
Line of Credit Facility [Line Items]
Interest paid, net of capitalized interest	$ 676,000,000	$ 577,000,000	$ 643,000,000
Commercial Paper
Line of Credit Facility [Line Items]
Average daily short-term borrowings	$ 2,700,000,000	$ 1,400,000,000
Weighted-average interest rate	3.07%	2.11%
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
Line of Credit | November 2018 Credit Agreement
Line of Credit Facility [Line Items]
Borrowings outstanding	500,000,000
Term Loan | August 2017 Revolving Credit Agreement
Line of Credit Facility [Line Items]
Maximum borrowing capacity										$ 1,000,000,000.0
Term Loan | 2017 Term Loan Agreement
Line of Credit Facility [Line Items]
Maximum borrowing capacity										$ 1,000,000,000.0
Term Loan | February 2017 Revolving Credit Agreement
Line of Credit Facility [Line Items]
Maximum borrowing capacity											$ 1,000,000,000.0
Revolving Credit Facility | August 2019 Revolving Credit Agreements
Line of Credit Facility [Line Items]
Maximum borrowing capacity				$ 500,000,000
Borrowings outstanding	0
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
Borrowings outstanding	300,000,000
Revolving Credit Facility | 2018 Revolving Credit Agreement
Line of Credit Facility [Line Items]
Face amount									$ 3,500,000,000.0
Revolving Credit Facility | Line of Credit | November 2018 Credit Agreement
Line of Credit Facility [Line Items]
Maximum borrowing capacity								$ 500,000,000
Loans Payable | December 2018 Term Loan Credit Agreement
Line of Credit Facility [Line Items]
Face amount							$ 1,000,000,000.0
Borrowings outstanding	$ 800,000,000
Unsecured Debt | Line of Credit | November 2018 Credit Agreement
Line of Credit Facility [Line Items]
Face amount								$ 500,000,000
Letter of Credit | 2018 Revolving Credit Agreement
Line of Credit Facility [Line Items]
Face amount									$ 500,000,000