Cover - shares	9 Months Ended
	Sep. 30, 2021	Oct. 25, 2021
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2021
Document Transition Report	false
Entity File Number	1-14387
Entity Registrant Name	United Rentals, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	06-1522496
Entity Address, Address Line One	100 First Stamford Place, Suite 700
Entity Address, City or Town	Stamford
Entity Address, State or Province	CT
Entity Address, Postal Zip Code	06902
City Area Code	203
Local Phone Number	622-3131
Title of 12(b) Security	Common Stock, $.01 par value, of United Rentals, Inc.
Trading Symbol	URI
Security Exchange Name	NYSE
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)		72,394,435
Entity Central Index Key	0001067701
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Amendment Flag	false