v3.25.2
Cover - USD ($)
$ in Billions
 12 Months Ended
Aug. 31, 2025
Sep. 30, 2025
Feb. 16, 2025
Cover [Abstract]      
Document Type 10-K    
Document Annual Report true    
Document Period End Date Aug. 31, 2025    
Document Fiscal Year Focus 2025    
Document Transition Report false    
Entity File Number 0-20355    
Entity Registrant Name COSTCO WHOLESALE CORP /NEW    
Entity Incorporation, State or Country Code WA    
Entity Tax Identification Number 91-1223280    
Entity Address, Address Line One 999 Lake Drive    
Entity Address, City or Town Issaquah    
Entity Address, State or Province WA    
Entity Address, Postal Zip Code 98027    
City Area Code 425    
Local Phone Number 313-8100    
Title of 12(b) Security Common Stock, $.005 Par Value    
Trading Symbol COST    
Security Exchange Name NASDAQ    
Entity Well-known Seasoned Issuer Yes    
Entity Voluntary Filers No    
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    
ICFR Auditor Attestation Flag true    
Document Financial Statement Error Correction [Flag] false    
Entity Shell Company false    
Entity Public Float     $ 475.2
Entity Common Stock, Shares Outstanding   443,179,176  
Amendment Flag false    
Document Fiscal Period Focus FY    
Entity Central Index Key 0000909832    
Current Fiscal Year End Date --08-31    
Documents Incorporated by Reference
Portions of the registrant's Proxy Statement for the Annual Meeting of Shareholders to be held on January 15, 2026, are incorporated by reference into Part III of this Form 10-K.