Legal Matters (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
Sep. 30, 2012
Legal Matters
Legacy CSK DOJ indemnity litigation reserve	$ 13.9

Aggregate carrying amount of reserve, as of the balance sheet date, for known or estimated legal fees pertaining to indemnity obligations.

No definition available.

Name:	orly_IndemnityLitigationReserve
Namespace Prefix:	orly_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration