Cover Page - shares	3 Months Ended
	Nov. 30, 2020	Dec. 31, 2020
Document Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Nov. 30, 2020
Document Transition Report	false
Entity File Number	001-36759
Entity Registrant Name	WALGREENS BOOTS ALLIANCE, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	47-1758322
Entity Address, Address Line One	108 Wilmot Road
Entity Address, City or Town	Deerfield
Entity Address, State or Province	IL
Entity Address, Postal Zip Code	60015
City Area Code	847
Local Phone Number	315-3700
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding (in shares)		864,041,635
Entity Central Index Key	0001618921
Current Fiscal Year End Date	--08-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
Amendment Flag	false
Common Stock, $0.01 par value
Document Information [Line Items]
Title of 12(b) Security	Common Stock, $0.01 par value
Trading Symbol	WBA
Security Exchange Name	NASDAQ
3.600% Walgreens Boots Alliance, Inc. notes due 2025
Document Information [Line Items]
Title of 12(b) Security	3.600% Walgreens Boots Alliance, Inc. notes due 2025
Trading Symbol	WBA25
Security Exchange Name	NASDAQ
2.125% Walgreens Boots Alliance, Inc. notes due 2026
Document Information [Line Items]
Title of 12(b) Security	2.125% Walgreens Boots Alliance, Inc. notes due 2026
Trading Symbol	WBA26
Security Exchange Name	NASDAQ