Cover - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2021	Feb. 18, 2022	Jun. 30, 2021
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2021
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	1-13461
Entity Registrant Name	Group 1 Automotive, Inc
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	76-0506313
Entity Address, Address Line One	800 Gessner,
Entity Address, Address Line Two	Suite 500
Entity Address, Postal Zip Code	77024
Entity Address, City or Town	Houston,
Entity Address, State or Province	TX
City Area Code	713
Local Phone Number	647-5700
Title of 12(b) Security	Common stock, par value $0.01 per share
Trading Symbol	GPI
Security Exchange Name	NYSE
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
Entity Shell Company	false
Entity Public Float			$ 2.7
Entity Common Stock, Shares Outstanding		17,040,503
Documents Incorporated by Reference	DOCUMENTS INCORPORATED BY REFERENCEPortions of the registrant’s definitive proxy statement for its 2022 Annual Meeting of Stockholders, which will be filed with the Securities and Exchange Commission within 120 days of December 31, 2021, are incorporated by reference into Part III of this Form 10-K.
Entity Central Index Key	0001031203
Amendment Flag	false
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY