Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2015	Feb. 22, 2016	Jun. 30, 2015
Document and Entity Information
Document type	10-K
Amendment flag	false
Document period end date	Dec. 31, 2015
Document fiscal year focus	2015
Current fiscal year end date	--12-31
Document fiscal period focus	FY
Entity registrant name	O REILLY AUTOMOTIVE INC
Trading symbol	orly
Entity central index key	0000898173
Entity well-known seasoned issuer	Yes
Entity voluntary filers	No
Entity current reporting status	Yes
Entity filer category	Large Accelerated Filer
Entity common stock, shares outstanding		97,189,417
Entity public float			$ 18,290,893,288