Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2019	Oct. 28, 2019
Cover page.
Document type	10-Q
Amendment flag	false
Document quarterly report	true
Document period end date	Sep. 30, 2019
Current fiscal year end date	--12-31
Document fiscal year focus	2019
Document fiscal period focus	Q3
Document transition report	false
Entity registrant name	O Reilly Automotive, Inc.
Entity central index key	0000898173
Entity incorporation, state	MO
Entity file number	000-21318
Entity tax identification number	27-4358837
Entity address	233 South Patterson Avenue
Entity address, city	Springfield
Entity address, state	MO
Entity address, postal zip code	65802
City area code	417
Local phone number	862-6708
Title of 12(b) security	Common Stock
Trading symbol	ORLY
Security exchange name	NASDAQ
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		75,658,897