Debt - Narrative (Details)	9 Months Ended
	May 31, 2019 USD ($)	May 31, 2018 USD ($)	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	$ 570,000,000	$ 450,000,000
Revolving credit facility | January 2019 364-day revolving credit agreement
Line of Credit Facility [Line Items]
Maximum borrowing capacity			$ 2,000,000,000.0
Borrowing outstanding	200,000,000
Revolving credit facility | December 2018 revolving credit agreement
Line of Credit Facility [Line Items]
Maximum borrowing capacity				$ 1,000,000,000.0
Borrowing outstanding	0
Revolving credit facility | August 2018 revolving credit agreement
Line of Credit Facility [Line Items]
Borrowing outstanding	0
Face amount							$ 3,500,000,000.0
Term loan | December 2018 term loan credit agreement
Line of Credit Facility [Line Items]
Face amount					$ 1,000,000,000.0
Long-term debt outstanding	$ 1,000,000,000
Letter of credit | August 2018 revolving credit agreement
Line of Credit Facility [Line Items]
Face amount							$ 500,000,000
Term loan | Maximum
Line of Credit Facility [Line Items]
Debt to total capitalization ratio	0.60
Line of credit | November 2018 credit agreement
Line of Credit Facility [Line Items]
Borrowing outstanding	$ 800,000,000
Line of credit | Revolving credit facility | November 2018 credit agreement
Line of Credit Facility [Line Items]
Maximum borrowing capacity						$ 500,000,000
Line of credit | Unsecured notes | November 2018 credit agreement
Line of Credit Facility [Line Items]
Face amount						$ 500,000,000
Medium-term notes | August 2017 revolving credit agreement
Line of Credit Facility [Line Items]
Maximum borrowing capacity								$ 1,000,000,000.0
Medium-term notes | 2017 term loan agreement
Line of Credit Facility [Line Items]
Maximum borrowing capacity								$ 1,000,000,000.0
Medium-term notes | February 2017 revolving credit agreement
Line of Credit Facility [Line Items]
Maximum borrowing capacity									$ 1,000,000,000.0
Commercial paper
Line of Credit Facility [Line Items]
Average daily short-term borrowings	$ 2,600,000,000	$ 1,400,000,000
Weighted-average interest rate	3.08%	2.00%