Cover - shares	9 Months Ended
	Sep. 30, 2019	Oct. 28, 2019
Cover page.
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2019
Document Transition Report	false
Entity File Number	1-13461
Entity Registrant Name	Group 1 Automotive, Inc
Entity Central Index Key	0001031203
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, City or Town	Houston,
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	77024
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 Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Shell Company	false
Amendment Flag	false
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Common Stock, Shares Outstanding		18,619,112